We didn't start our DD in preschool until she was 3. She is now 4 and finally interacting more with her classmates. Up until this past week she was content with swinging at playtime. She had her preferred swing and all the kids knew not to try to take it. But this week she is playing with the other kids. This took over a year! She also doesn't talk to her full potential at school but even that is getting better. I think it just takes time.
This said, I do agree with Grinity in that you should try a few options and always be willing to put her some where else if you don't feel the school is a good fit. The positive from your post is the end of the day pick up time when she shares with you about her day. She might not be interacting but she is clearly paying attention, plus it seems that she is happy about the stories she shares.
