I can't believe Miley tried to use tongue though, even though it's not clear if she did or not but that's probably why Katy backed down. She looks surprised
Tbh, it is a bit disrespectful to make out with someone who is in a relationship. Doesn't matter if she's a girl, because if Miley were a man, it would be unacceptable.
I bet Katy went with it initially because she thought it was going to be a little peck, but then Miley had to go for the tongue. I really don't get why Miley does stuff like this.