11year old friendless and just realising she may have autism

Hello everyone 

My daughter is 11 she has always been very very quiet. Doesn’t mingle with other kids or chat. She doesn’t seem to be able to have a conversation . She had one best friend who has now again dumped her. 
In a class of 33 not one child wants to sit with her. At family social events she will mingle for 15 mins and then sits with us quietly. With other parents asking what’s wrong and I get quite anxious about it. 

it appears that she is socialising when kids are playing , she laughs or gives one word answers but she never speaks or gives opinion. Or stands up for herself if anyone says anything mean. Her teacher says she’s comes across “as shy”

she loves to dance and be on stage . Dancing because she doesn’t have to speak. 
She is confident speaking on stage because the words are there for her to say as learned beforehand. So this again masks what I am seeing from a socialising side compared to other adults/ teachers . 

She is fine at home with us, wicked sense of humour. It’s a shame she usually different around non family . She can’t even give more than a 2 world answer to neighbours she has know for several years. Doesn’t speak to her dance teacher she had had for 4 years . 

It is sad to see her at a recent disco having not one child to dance with, and no one spoke to her. I think children get bored with her as they try to chat but she doesn’t chat back.

Does this sound like anyone else’s child ? I feel bad that I may have missed on having autism and could have got help years ago. I only found she may have autistic traits when I was googling situational mutism