15 year old daughter struggles to socialise

Okay, so 

For nearly all of my life and this is still true now, nearly all of my friends are contextual and I only like hanging out with them in those contexts. So if it's a school friend, I honestly have no interest in seeing them outside of school. Does your daughter actually want to socialise in the way you think she should? If not, it might be you that needs to moderate their expectations. I actually became much happier when I could just settle down with a few good friends and my teachers stopped setting me 'make more friends' targets.

If she wants to try socialising outside school, here are some things that help me.

I socialise best with activities, so having something to do like crafts or on a walk or cooking. Just 'hanging out' does not work and stresses me out massively. Think about an event that also has a hard ending, so that ending the visit is not an additional stress while she's starting out. Maybe a walk with a set route before hand? Baking a cake and having tea together? Doing a sporting or music event together if that's something she enjoys? Something that is at least vaguely related to her interests to help regulate. 

Also doing it in controlled environments and only with maybe 1-2 people at a time helps because I'm not trying to manage sensory stress as well as the socialising. Going into town to go shopping leads to me becoming minimally verbal and walking into strangers on the street very quickly. 

Does she have any hobbies or clubs she goes to like music, sport, or other things? This is now how I make most of my friends, and again they're nearly all contextual, but it's another way to socialise outside of school?

Okay, so 

For nearly all of my life and this is still true now, nearly all of my friends are contextual and I only like hanging out with them in those contexts. So if it's a school friend, I honestly have no interest in seeing them outside of school. Does your daughter actually want to socialise in the way you think she should? If not, it might be you that needs to moderate their expectations. I actually became much happier when I could just settle down with a few good friends and my teachers stopped setting me 'make more friends' targets.

If she wants to try socialising outside school, here are some things that help me.

I socialise best with activities, so having something to do like crafts or on a walk or cooking. Just 'hanging out' does not work and stresses me out massively. Think about an event that also has a hard ending, so that ending the visit is not an additional stress while she's starting out. Maybe a walk with a set route before hand? Baking a cake and having tea together? Doing a sporting or music event together if that's something she enjoys? Something that is at least vaguely related to her interests to help regulate. 

Also doing it in controlled environments and only with maybe 1-2 people at a time helps because I'm not trying to manage sensory stress as well as the socialising. Going into town to go shopping leads to me becoming minimally verbal and walking into strangers on the street very quickly. 

Does she have any hobbies or clubs she goes to like music, sport, or other things? This is now how I make most of my friends, and again they're nearly all contextual, but it's another way to socialise outside of school?