Long story short: There are two girls: Lynda & Mary and they are good friends, I don't like Lynda and im chatting with her only to get with Mary. Sadly, Mary is interested in my friend and hes kinda getting interested in her too.

So we decided to meet all together at school dances next friday and i know that my friend gonna try to pickup Mary and that pissed me off a bit.

So i have some questions about that situation:
1. I already told my friend that im gonna help him to pickup Mary by izolating Lynda, but is there any way for me to izolate him?
2. Some guy already told me that i have no chances with Mary, so if ill izolate Lynda what should i talk about? I mean i need some topics, because i know her a little and i can't use normal openers.