M.T.
It's hard for a 2 year old to understand the difference between sharing (your choice) and having something taken away. I remember some time back, a mom here taked about sharing and how she always made her child give the other kid the toy - but that isn't sharing, it's just being taught that you're always last and your feelings never matter - this mom's complaint was that other parents didn't make their kids give her toddler their toys if she wanted them, she thought they weren't "sharing."
There's a difference between sharing and taking turns. If it's a communal toy, and the other child wants it, I'd tell your daughter "one more minute, then it's Henry's turn." That's taking turns. Sharing means they are playing with the same thing together. I'd be sure to use the terminology that way, so she knows when she's sharing and when she is going to need to give someone else a turn with a toy. It's absolutely fine to teach her to say that she's not done with something or that the other child can have a turn in a minute, but at 2, she is too young to grasp that concept and needs you or whomever is the adult in charge to step in. She may feel powerless to say "no" or that to do so would not be "sharing" as she's taught. She does need to know that sharing doesn't mean having her toys taken away, and it's important to get other parents involved, so that if their child is taking something from her, they should be the one to tell their child to ask if he can have a turn and to keep him calm as he waits a reasonable amount of time for his turn