Guilt. Stress. Unaware of what to do

okay so to start this, I know I am in the wrong. I have no one to blame but myself for this and I'm suffering from an intense feeling of guilt as a consequence. I have an online platform that I talk with people who want sexual favours, thing is I lied about my age. I have been doing it just for attention and to feel desired for once but i know now that theres other ways to go about it. As far as everyone was aware i was 18 years old, which is not the case. I am 2 years younger than that. I had been doing this for months and met a girl 8 years older than me who I talked to back and forth just sexually. Until it progressed more than that but I didn't think it would get serious and I wouldn't have to confess I had lied about my age and I wasn't who she thought I was. I went on with this lie for months and I didn't know how to back out of it. It kept getting more intense and she has become dependant on me. She is suffering severely mentally and I am the only person she has who supports her and loves her. Thing is, I can't continue this with her. For my sake but also hers. I cant just leave her because she won't be able to cope by herself and I've grown to truly love her. She is a truly outstandingly caring person who has shown me true affection and I don't know what I would do without her either. She's getting very invested in the relationship and I know if I keep this going any longer it is going to hurt her a whole lot more. I don't know whether to keep this going until I am able to slowly slip away and she can stay stable or if I quickly cut it off or if I tell her the lie I've kept up with for 4 months. I feel so guilty. I feel so awful about myself. I am avoiding leaving the house, I quit school, I dropped all of my friends and I wallow in my own guilt all day. Its not healthy for me to keep up with this lie for me or her. I'm so stuck. I cant talk to anyone about it. There is no one.