Tanya is first introduced in episode 10 of season 5 ("South Side Rules"). Debbie joins Derek for a family picnic where she meets Tanya who she initially thinks is Derek's sister but as it turns out she's his sister-in-law and she's related to Derek through the child she had wit his older brother, Jake. She reveals in her conversation with Debbie as she paints her nails that she doesn't get along with her real family as her father's in prison and her mother's an alcoholic, but once she met Jake and had Miles the Delgados accepted her like one of their own.
Tanya appears in episode 2 of season 5 ("#AbortionRules") and her attitude towards Debbie has obviously changed. Debbie appears at the nail shop where Tanya works asking of Derek's whereabouts and why she can't seem to reach him. Debbie is confused about why Derek and his family have been so distant towards her because when Tanya got pregnant with Jake's baby they accepted her with open arms. Tanya then begrudgingly tells Debbie that it wasn't Derek's parents that made him move to Florida but he wanted to do it himself because he wasn't ready to be a father. She explains that Debbie scared him among other things about Derek that she didn't know because Debbie never truly took the time out to get to know him. She then ends it with saying that "Guys like to feel supported. Not trapped." When Debbie tells Tanya that she didn't mean to "trap" Derek, Tanya shows some understanding but in the end holds true to what she said before.
Tanya appears more throughout season 7 and plays a more significant role in this season. In episode 5 ("Own Your Shit!") Tanya is first seen bumping into Debbie on the streets with Franny where Debbie is pretending to be homeless unbeknownst to Tanya in order to gain money so that she can remain in the Gallagher household due to Fiona threatening to put her out if she doesn't have rent money. While Debbie is thrilled to see her, Tanya is obviously uncomfortable with this because she essentially thinks that Debbie and Franny are homeless with nowhere to go. When their conversation ends Tanya tapes Debbie on her phone beating up a homeless lady who threatened to take Debbie's spot. It is then in the episodes to follow that show that Tanya took the footage to DCFS (Department of Child and Family Services) and Debbie then has to prove that she's a capable mother.
In episode 8 ("You Sold You the Laundromat, Remember?") Debbie shows Ms. Delgado and Tanya around her and Neil's home to show that she has a good place for Franny to stay and that she isn't indeed homeless. Tanya and Ms. Delgado are happy to meet the baby but they obviously aren't to keen on Debbie herself. Later on the episode it is revealed that after they left Debbie and Neil's house they came back when Debbie was gone and kidnapped Franny.
The last episode Tanya is seen in in season 7 is episode 9 ("Ouroboros") where she and Ms. Delgado are with Debbie at the DCFS meeting in order to gain custody of Franny. In the end Debbie still holds custody over Franny and Tanya and Ms. Delgado are granted visitation.