She's insecure as fuck and craving the attention and feeling of being wanted that a relationship provides.

Nothing wrong with that. We all go through it. We all need attention.

She's just going about getting it in the wrong way. Trapped from 16 to 18 in a high school relationship, she has some catching up to do and her expectations are going to be a bit different since she hasn't had any time to herself, single, to figure out who she is right now and what she wants or where she is going.

Be honest but not harsh with the messages. You can throw her a bone - wow you got the boys coming to your yard lolol - but if she shows you the messages that often as a look at me thing, find a cooler response. She's a woman. She's a young woman. She's going to get attention. She needs to learn to thrive on the right kind and not get caught up in sweet words from manipulative dumbasses. She needs to learn it's not exciting to have someone you're not attracted to feeding you this attention.

That lesson she might have to learn through experience, though. Getting used for sex or dropped immediately if she won't put out is inevitable if she keeps going.