Daya lived with her mother, Aleida Diaz, and four younger siblings, along with her mother's drug dealing boyfriend, Cesar. Daya served as the main caregiver for her siblings while her mother was treated to expensive dinners and outings with Cesar. This created resentment from Daya towards her mother. After Aleida was sent to prison for taking the fall for Cesar's drug dealing, Daya assumed even more responsibility for her siblings. They visited Aleida in prison, but Aleida took no interest in them, instead asking if Cesar was cheating on her. She accused Daya of sleeping with him, which angered Daya. However, Daya later initiated a sexual relationship with Cesar in retaliation against her mother.
On her first day, she arrives to Litchfield along with Piper and Watson. Upon her arrival, she is slapped by her mother. Gloria Mendoza is assigned to be her mentor, but Daya is criticized by her for not being able to speak Spanish. Daya initially clashes with Maritza, who is Aleida's adopted daughter in prison. She is not fully welcomed into the group until she and Aleida agree to a truce. Daya threads her mother's eyebrows in exchange for being allowed to sit in on the games of dominoes.
Daya strikes up a romance with C.O. John Bennett which they must conduct in secrecy as relationships between inmates and C.O.'s are forbidden. The two conduct their relationship by passing notes and drawings to each other and meet in a janitor's closet for sexual encounters. Daya discovers Bennett's prosthetic leg but assures him that his disability does not matter to her. Aleida discovers their relationship and tries to steal away Bennett as revenge for Daya's relationship with Cesar, but Bennett refuses Aleida's advances, much to Daya's relief. Daya eventually becomes pregnant and decides to keep the baby, which creates trouble for her and Bennett. If Bennett is revealed as the father, he would be imprisoned for rape as under the law, inmates are not allowed to give consent regardless of their willingness.
Bennett attempts to arrange for a furlough for Daya, which would give them a cover story for her pregnancy--they would explain that Daya has sex with someone outside of prison and thus Bennett would not be suspected as the father. However, Aleida points out that no one ever receives furlough and she works with Gloria and Red to a concoct another plan to explain Daya's pregnancy.
Eventually, they decide that Daya will seduce Mendez and collect evidence of the sex to claim Mendez raped her. This will provide a father for Daya's child and will oust Mendez and his drugs from Litchfield, which would benefit Red. Daya manages to interest Mendez by asking about his day but she fails to save the condom from their sexual encounter. Aleida, Gloria, Red, and Red's girls arrange it so Caputo walks in on Daya and Mendez having sex and their plan finally succeeds. Unfortunately, since Fig wants avoid any more scandal, Mendez only receives a suspension.
Daya's pregnancy is still not common knowledge and she is helped by Gloria and Aleida, who compete to fill the motherly role in her life. She becomes irritated with Bennett for not taking responsibility as the father of her child. Daya also worries about the health of her child while she is in prison and Bennett attempts appease her by smuggling her in fresh foods. She and Bennett fight off and on throughout the season and she becomes angry at Bennett when he throws Maritza in SHU for attempting to blackmail him.
Mendez continues to send letters to Daya, which makes Bennett uncomfortable. They make up by Valentine's Day although their reunion's happiness is short-lived when Mendez returns to Litchfield. Daya begins to have second thoughts about naming Mendez as the father of her baby, claiming that she wasn't thinking straight when Red and Aleida talked her into the plan and doesn't feel comfortable sending an innocent man to prison. Eventually, she reluctantly gives a statement to Fig and Caputo that states Mendez as the father of her child. Fig harshly tells her that she has ruined a man's life for encouraging his advances, which causes Daya to feel even more guilt. "In my neighborhood, real men stand up and claim their kids," she tells Bennett. Tired of Daya's fickleness, he asks her what she wants to do. "I don't know," she says. "But this doesn't feel good." When Mendez is arrested, he asks Daya to wait for him and proclaims his love for her. Daya tells Bennett that even though Mendez is a horrible person, at least he is not ashamed of her, which prompts Bennett to confess to Caputo the truth.
Daya also joins the staff of Piper's in-prison newsletter, "The Big House Bugle" as a cartoonist. She makes comics about the Litchfield staff, where she portrays them as animals, which many of the inmates and staff find funny.
Dayanara is mostly quiet and shy although she is a fierce protector of her family and is not afraid to stand up for herself. She does not speak Spanish, which draws the annoyance of Gloria. She enjoys drawing manga even since she found a manga book in the trashcan at a young age. She proclaims the characters to be "more beautiful than Disney princesses".
Daya is shown care deeply for her siblings--always cooking for them, disciplining them, and taking an interest in them and their activities. She attempts to reprimand Aleida for ignoring her children, but is often ignored. She is eventually welcomed among the Latina inmates and they often enjoy teasing her, much to her annoyance. She holds an idealistic view on love, unlike her mother.
In season 2, she begins to feel guilty for framing Mendez as the father of her child and constantly flip flops between wanting Mendez to walk away free and not getting Bennett into trouble.
She has a much shorter temper during her pregnancy and is quicker to impatience and irritation, which causes Bennett to compare her to her mother, much to Daya's displeasure.
Dayanara has dark brown eyes and brown wavy hair with dyed blonde streaks. She is of average height and has a curvy figure.
- John Bennett (boyfriend and father of unborn child)
- George Mendez (fake affair)
- Cesar (ex-boyfriend)
- "Fuck diamonds, I got spinach!"
- — Dayanara Diaz, Hugs Can Be Deceiving
- "I don't fuck dudes for Big Macs."
- — Dayanara Diaz, The Chickening