My boyfriend invited me on a double date with his best mate and his girlfriend at the request of the girlfriend who was keen to meet me. The double date didn't go as well as I'd liked - I immediately noticed a flirty vibe between the girl and my boyfriend that surprised me. I thought she was flirting quite blatantly and even started talking about herself being naked and skinny dipping totally out of context 
But I met her again recently and was willing to wipe the slate clean. She seems friendly enough when we talk, but I noticed that even though she's smiling with her mouth her eyes are constantly looking me up and down. Makes me so uncomfortable! And we don't click.
Worse, she was flirting with bf again. When he walks into a room she looks like she wants to jump him - it's not subtle at all. She even had him water her plants when she was on a 2 week holiday recently.
Now my boyfriend has been pushing me to spend time with her while he spends time with her boyfriend (his best friend). When he has a day out with the guys, his best friend sometimes brings her along. He said 'I think you'd really enjoy hanging out with her'. Or at a recent get together where I didn't know many people, he told me to go and look for her! I simply told him no.
The thing is I would gladly double date with some of his other friends and girlfriends who I don't feel are carrying a torch for the boyfriend or making me uncomfortable. But how do I broach this without looking like the bit*h in the situation?