How to deal with this?

So there’s this girl in my lunch period who’s nice but became very clingy very fast... it’s gotten to the point where she can’t stand to be alone for one second, she’s always gotta follow me whether it’s to the bathroom or to fill up a water bottle and spam text me before I can even meet up with her and is always watching what I’m doing or notices when I’m not giving her my full attention (like if I’m doing HW). If I’m gone for even a minute she seems upset that I don’t tell her my whereabouts like you’re not my mother? It’s bothering me to the point where I feel like I have to hide from her. I don’t even go into the lunchroom anymore it’s so bad. She’s very antisocial though and has few friends but none who has the same lunch with her. I mean I feel bad but it’s also kinda becoming too much for me and I can’t deal with it anymore. I could tell her how I feel but she would get very mad and I’m scared of what she would do. Please help me :(