As far as the socialization goes, I wouldn't be too concerned. I would just continue to take her to places like the playground, playgroups, classes etc, but not force her to do anything that she isn't comfortable with. My daughter was the same way. She takes gymnastics class and when she was 2 we did the mommy and me class. It took her almost 2 whole sessions, which was about 6 months, before she would even take part in the warm up activities. At storytimes at the library, she would just stand back and watch and never participate. If a child approached her to talk to her she would turn and hide her head in my legs. She is now 3 1/2 and is a social butterfly. I think she just needed to come into her own. My will be 2 in Oct. and he doesn't participate either. I don't worry because I know he will eventually.
I can't really give any advice about her sleep issues. I'm lucky that my kids are pretty good sleepers. Is there anything new in your daughters life or anything that she needs to adjust to? What about teething? For several months my daughter dealt with her 2 year molars coming in which caused problems sometimes. When my daughter transitioned to a toddler bed she kept getting out of bed and wouldn't go to sleep. I would just pick her up, tell her I loved her, and put her into bed. I would tell her that I would be back to check on her, but she needed to listen to her musical seahorse and keep her eyes closed until I came back in. She would end up falling asleep waiting for me. This took about 3 weeks and then she started going to sleep on her own. I know that that is different from what your daughter is doing, but maybe if you tell her you love her and that you'll come back to check on her it will help.
Good luck, sorry this is so long!