1. Sam is highly resistant to that sort of thing, but not immune. Happy to talk it out on a case-by-case basis.

2. Yes, but there are some serious consequences. A vampire who feeds off of Sam's blood becomes "blood bound" to her. It's a three-step process. The first time, the vampire starts to daydream about Sam, in a high school crush sort of way. The second time, the vampire finds it difficult to act against Sam's wishes. The third time, the vampire is basically Sam's thrall.

3. No opt out necessary. But please take a look at my permissions.