Me and this girl that I met at are really close, yesterday we all went clubing, I was with my friends and she was with hers. She was completely out of her head, so I went to look after her, her friends wanted me to look after her so I did, I went and got her some water, and as I came back she was sat with a guy and kissing him, although were not together, it really got to me, we're both really flirty together, sleep in the same bed (but don't have sex). Should I be angry at her? Shall I let it go?