How should you handle a more attractive women then the one you are interested in cock blocking you?

I find the objectively hotter one a fucking shit stain of a human being while I am really attracted to the less objectively attractive one. The less attractive one seems to not want to flirt with me when we are all together but alone. She flirts heavily, major IOI'S etc. But I can't always get her alone.

Its almost as if she feels she can't compete. I'm not sure what I can do?

Edit: Thanks for the advice everyone. I will try to isolate and see how it goes.