AITA for feeling drained by my friend who depends on me for everything socially?

My friend, who I’ll call Elle (18F), and I (17F) go to the same high school. She’s been at our school since kindergarten, but she doesn’t have many close friends besides me. I transferred in 9th grade and made an effort to put myself out there, especially through marching band, so I’ve built friendships in several different groups.

Elle, however, limits herself socially to hang out with certain groups, calling band/theater kids "weird", popular kids "fake", and sports kids "cocky". Because of this, I've become one of her only social connections. Shes also very dependent on me, she wont walk into practice, get lunch, or even get water by herself. She'll wait in her car until I arrive and follows me everywhere, making it hard for me to have friendships or time that dont include her.

Some of her behavior also comes across as passive-aggressive or inconsiderate. At lunch one day, she wanted to sit in a specific spotted kept whispering at me to move even after I explained I couldn't.  When she didn't get her way, she made a backhanded comment about her seat. Another time, she took my seat while I was gone and asked if we could "share a chair" when I came back. When I said no, she still didn't want to move, and my friend and I ended up awkwardly squeezed together while Elle sat between us, making my only free time during the day uncomfortable.

There's also another girl, Lennox, who used to be close with us. Over the summer she distanced herself and clearly doesn't want to hang out anymore. Despite this, Elle keeps chasing her. Recently, Elle asked me multiple times to go with her to talk to Lennox, even after I said no, and then stormed off when I wouldn't go.

All of this has been building up, and I feel emotionally drained. Elle isn't a bad person, but her codependence is affecting me, and I feel like I can't breathe socially. I want to set boundaries and regain some independence, but I'm afraid of hurting her or seeming like I'm abandoning her.

So AITA for wanting to set boundaries and take space, even if it makes her feel abandoned?