A little bit ought not hurt her...
As for brain freeze, they make ice cream FOR dogs, I sincerely doubt that's a big concern.
And especially not in small amounts.
Onions and grapes are bad, though, make sure she doesn't get into those!
And, of course, anything containing caffeine.
*cleaned up lots of dog puke because we have a dog with an obsession with stealing our coffee*
Our biggest problem, though, is making sure our dogs have enough water during these warmer months...