I had the same situation before

I tried to be more active to build the relationship, and I found it did not help. Then I changed my way to treat them, and I considered them as air. Guess what, both of them tried to talk to me later on. The secret was that I seem had good relationship with their boss and other peers. They might feel the pressure.
If she is the only one cold face to you, then she is only one you cold face with. You show even more warm face to other people.