She is NORMAL.
MANY kids do this.
It is developmental.
Also, kids this age do not play interactively.
They do what is called "parallel play."
She's fine.
Let her be herself... my daughter was like that. And you know what? She is now 8 years old, and is very Wise beyond her years. She is an 'observer' and has very very spot on ability to discern other kids/people/intentions. Much more so than other kids her own age. Even her Teachers say so.
Let your child, develop her own personality. Not according to what other people think she should be.
Nurture HER. Her own talents/interests/disposition etc.
It will serve her well.
Not every kid 'has to be' an extrovert or interacting like a clown.
My kids, though very well adjusted, are not like that. They CHOOSE who they play with and CHOOSE what kid they want to play with... according to character etc.
That is a good thing.
So, your daughter is young. Allow her, to gauge herself too and with your guidance, to just TRUST herself and you, and just have fun. Even if that means 'staring' at the other kids. For now.
Let your child, be herself.
That is the greatest 'gift' a parent can do.
all the best,
Susan