Is this rude? My friend invited me over to her house where her HUSBAND was walking around naked?and?

That's tricky. She should have told you before hand about that, or at least moved to a different room since it made you uncomfortable. You can't really tell them how to behave in their own home but they definitely should have warned you. Just don't go over there anymore and have visits at your house, but also let her know how you felt so it doesn't seem like you're not open to her culture.