Have you had a meeting with her teacher? I would also ask them for suggestions on what can be done.
My eldest DS ( 9yrs old) is very shy and introverted but his teachers have been very supportive and this year his teacher ( who was new to the school and did not know DS's school history) was stunned to hear what DS used to be like.
He still is shy and introverted but handles school pretty well overall.
Things that worked for us:
outside of school activities especially things that are a little niche so he could feel he was brilliant.could contribute a lot to them. It really boosted his confidence when he developed a reputation as being really good at a particular skill at a club he attended
Also we encouraged him to do powerpoint presentations to his class (show and tell time) about his hobbies and what he loves. I would help him do the powerpoint and we'd rehearse at home. Because he picks a topic he loves - he felt ok about discussing it in front of the others and taking any questions. Now he does a few presentations a year to his 'audience' !
He stopped being the invisible child. Other children would go home telling their parents about to subject of his presentation and it seemed to step him up a gear. I would have parents saying " oh are you minipancakeflipper's mum?"
Our school have a friendship tree. Underneath are log seat and if lonely you go there.
The extra-curricula keeps my DS1 going. He had a crap day yesterday at school so I let him go out on his bike for 30mins and he headed off to see if boy who lives up the road from the year below was around to join him. And happy mood was restored.
Are there any other issues with her behaviour that might be hindering her? Is she a bit of a perfectionist? Does she put others on a pedestal? Does she view herself as inferior?