Throwaway Account

I (20f) recently discovered that my aunt (42f) is actually my mom and my dad is actually my uncle who adopted me with his wife. I'm hurt and I want answers.

Years ago, my paternal aunt (technically mom) was reckless as a teen and got pregnant with me by my mother's half brother. My aunt wanted me to go to another family and have a closed adoption but my paternal grandparents (technically maternal grandparents) convinced her to allow my mom (technically aunt) and dad (technically uncle) to adopt me so that way I would be close if she ever changed her mind. I guess my aunt did because for a few years she didn't speak or see anyone in the family for years, but then she came back and re-established contact.

I was told all of this by my grandma (my mom's mother) because she has cancer and wanted me to know the truth. I couldn't believe what she was saying because my aunt and I don't have a relationship and she's always been so distant from me. I have an older sister (technically my cousin) who my aunt loves, spoils, and has almost always been there for. Example: I can count on one hand the number of recitals, award ceremonies, etc. my sister had that my aunt (technically mom) missed since she was 8, while I can only think of three times in my entire life that my aunt has seen anything of mine.

I also have two other cousins (my grandparents have three kids) and my aunt has taken them on out of town trips to theme parks, beaches, shows, etc. and my sister has had overnight sleepovers with my aunt. I never got anything like that and if I asked my parents would just say that my aunt just had a different relationship with my sister and cousins than I did and to give it more time. When I asked my aunt directly, she would say that the world isn't fair and accused me of being greedy and entitled. That really hurt me as a kid because I used to really look up to my aunt. She's beautiful, smart, successful, stands up for what she believes in, and has always been so well put together.

I used to think that there was something wrong with me, so when my grandma made this confession, I went straight to my mom about it. She denied it but later that night my dad took me on a drive and confirmed what my grandma said. I was in disbelief and wanted a DNA test but my dad said that it may be of no use since we all are technically related. I wanted to talk to my aunt about it but she recently moved away and has deleted her social media and changed her number. She and my mom had an argument about giving me college money so my parents don't have her new address or phone number.

My grandparents are celebrating their anniversary next weekend and my aunt will be flying in for that. Whether privately or publicly I want to confront her but my sister thinks that ruining our grandparents party isn't worth it and wants me to wait for her to try and convince our aunt to talk to me at a later time. I don't want to spoil my grandparents' moment but I'm also so hurt, confused, angry, and anxious about this all so I have to ask AITAH?