I'm thinking of taking back the tv I gave to my sister
Why would you take the TV back?
She's so ungrateful. She never says thank you nor even comes to dinner with us.
I don't think you should take the TV back. I understand you are angry at her for not showing for dinner, but taking the TV would make things worse for the both of you.
I always get f**ked when trying to do something good. If she's going to treat me this way, then I will take the TV back.
You gave your sister this tv as a gift and clawing it back from her is a breach of your intention to do something nice for her. Let go of your resentment about not getting anything from her and just enjoy the joy the tv gives her.