Too much flirting

Went away with my boyfriend (Neil), his mate Dave and girlfriend Natasha. I noticed Natasha and Neil (my boyfriend) would flirt with each other a lot yet they both moan about cheats and flirting. There was lots of innuendos being said and facial flirting! This annoyed me as they contradicted their opinions.

Natasha and Neil then mentioned a guy we know called Sam and said I should stay away from him as he has tried it on with me - this isn't the case Sam has never done that and they think having a conversation means he has bad intentions. They don't like it as Sam gets on well with me out of them all.

I think Dave is a nice good looking guy but wouldn't cross the line and I remain polite to him vice versa. There is awkwardness there but its not worth going down that road.

Also when I went to the shower today Neil was slagging me off to the others as I was killing flies last night saying there was no need. I didn't want to swallow them in the night, I think he was jealous as he friends were in stiches by my antics. I found out he slagged me off from Natasha. Natasha annoys me cos I didn't need to know that and she keeps mentioning Neil's ex who I didn't like. I don't know if she is being devious as she tends to make comments like 'Neil is being funny with you etc' when he is probably tired but says things in a funny way.

Is Natasha trying to split us up and is Neil looking elsewhere? Sorry of this sounds a childish problem but I don't know if I am overreacting or is their behaviour is a bit out of line.