Like Mystifying says, children don't need others to play with until later.
May I quote a few lines from a book I love?
"Again and again all researchers come to the conclusion that what a child needs if s/he is to develop to his/her optimum on all levels- and this includes social development- is a warm, happy, fulfilling home life especially during the early years".
There was also a report by the Lady Gowrie Child Centre some time ago called A Must, A Maybe, or A Mistake- Parents and Toddler Groups. It summed up by saying that groups meet the needs of parents to socialise- not really the toddler. It says that there is no need for formal play groups for under threes as asking them to share, cooperate and get along is not part of their world. (Not to say that we can't started to introduce the concepts).
So it sounds like your DD Shellbell gets plenty of opportunities to socialise. She is still most interested in mum and will be for some time...