M.B.
As long as you see that she does interact well with people when the opportunity presents itself, you probably shouldn't force her to do more. Some people feed off of being with other people and it energizes them...others actually use up energy when they are with others. She may need more alone time than you and that's okay. It doesn't mean there's anything wrong with her. She's just wired differently. It sounds like she's a "normal" healthy introvert. You don't want to start sending the message that there is something wrong with her. That CAN cause problems! Let her be herself, so long as she's healthy and wellrounded...and it sounds like she is.