While I don't want to explain the comic, I also don't want to leave people hanging due to losing a game of "don't get the reference", so...

1. Hypnosis via watching a swaying object
2. Mind control via SCIENCE!
3. Evil twin from a mirror universe (Star Trek reference)

And yes, evil mirror universe Susan would like hugs. Obviously.

Susan is... She's acting out of character in a very in-character way? She knows better than to just hug someone like this without previously established hug protocol, but she's also experiencing a sort of high due to the freedom from her usual anxieties (and knowing this is non-canon). She's a bit more impulsive than usual, and I feel that's natural under the circumstances.