Dating Etiquette

It's funny.
There is someone in my life who is a "serial dater", and we seem to have very different outlooks on what is acceptable when it comes to dating.

I, for instance, do not think it is alright to invite one person over to spend the night, meanwhile, "date" another person.

I think the correct term I am looking for:
Dishonest. (there were a couple other ones but I didn't feel comfortable writing them. I still think them though)
Then again, I'm not being very honest when I'm nice to her when I'm around her.

You don't "date" people by sleeping around. That's sneaky, manipulative, and just wrong.

Erg.