It's because Sally Sparrow was wandering around London without an umbrella for the entire episode. I don't know why she didn't have one--maybe it would block her view of the Weeping Angels just long enough for them to get her. Whatever the reason, the result is many damp screencaps.

Would she fight it or get sucked in?

Good question. She might be able to fight the suggestion for a minute or so before finally getting sucked in with the rest of them. Since while she is an empath and absolutely loathes having her head messed with, she's still very vulnerable to mental attacks.