why do i care for the people who hurt me most?

so here i am. tired as fuck and im at my friends house, and im always the first one asleep so my "friend" and my sister thought it would be funny to draw on my face while i was sleeping. its not like this wasnt the first time it happend and they know i get mad when they do it. but they thought theyd be "smart" and try to clean it off before i woke up. well they must be purly stupid of they think they could do all that and have me still be sound asleep. now im not even sure if i want to stay friends with this girl cause shes been acting more and more like a bitch and has been treating me like shit. thats all i feel like nowadays. for example after swimming this bitch and her "bff" were taking me home so we went to taco bell for dinner and them to sat at one table with the bitches mom and step dad and i had to sit all alone. i felt like locking myself in my room and crying. i mean they didnt even see anything wrong with it. i feel like half of me wants to ditch them and the other half wants to stay friends with those bitches . so i have one question, why do i care for the people who hurt me most?