Can she discard "bad" followers to gain life such as the poltergeist?

Thanks!

Yes. The only thing she cannot do with so called "negative" Followers, is ditch them on her space; anything else is fine.

If she steals a character's follower after landing on him, can she still engage that character as usual?

If she steals a character's follower after landing on him, can she still engage that character as usual?

No. The rulebook states either attack another character or use one of your abilities on them.

Vampiress is one of my favorite characters. But I tend to not eat my followers when I am playing her. (not hungry enough?)