when I’ve tried to break it off in the past (due to DC and not being ready to move on with someone new) she’s sent me streams of pictures of her absolutely crying her eyes out
She's done WHAT?! This is awful behaviour on her part. SO manipulative. MASSIVE red flag.
she really is such a sweet person
Yeah, the thing is, she really isn't.
All these 'sweet' and 'nice' and 'caring' things she does are not actually for you. You really need to stop framing it as her wanting to make you happy. That isn't what it is. She's doing it for herself because it makes her feel like she's a saintly caring person, and that in turn makes her feel superior.
I'm guessing that she actually bloody loves it when you're unhappy or sad about something (eg your friends) because she then gets to enjoy comforting you and telling you that you don't need them because you've got her to look after you.
It's all manipulation, OP. She might not even be aware of it herself, but that is absolutely what it is and you need to run for the hills. This relationship is going to be hellish if you continue it.
I suspect when you break up with her (because you DO have to break up with her) she will become hysterical, angry, accuse you of ruining her life, will bombard you with messages that will alternately be sweet/calm and then overwrought/distressed, will keep badgering you to meet for 'closure', may threaten to harm herself, etc. DO NOT be taken in by it and DO NOT stay in contact with her.