My middle dd (12.5, Year 8) has been really miserable this evening as she had no Halloween plans. She tried a few friends, they were either away for half term or had plans and no suggestion that she could join 
To make things worse, dd1 went T or T ing with friends and then came back here for pizza. Dd1 did offer that middle dd could go with them which was nice for her but she didn't want to. I think the real problem for dd is that she thinks everyone is having a brilliant social life and she doesn't. I know social media is partly to blame for this and I have suggested that dd either comes off Instagram or takes it all with a large pinch of salt, but dd says they all talk about what they get up to at school as well.
Dd does have some nice friends but she isn't really in a close group or has one best friend, either of which I know she would like. She (or I) always seems to instigate any social arrangements and I think she's finding it all hard work.
Dd is very sensitive and takes it all to heart. I try and be supportive but I just don't know how to help her.