Problem of friends

I have 2 female friends........ One of them is very close friend to me from last 6 month "A"....and second become close now days "B".... and both friend know I like "B" but "B" not give me any response for relationship but trust me a lot ....The problem is that i was talking With "A" on mobile messaging and use some cheap world for "B". "A" accidentally send this message to "B". Now "B" come to me she didn't know with whom "A" is talking and told me about that message...And she only share that problem with me.....She thought that "A" is against us.... By th way both I and "B" notice that "A's" behavior is change when we both come closer mean trust on each other.....And day by day situation is going wrong ......In that situation what i do because i don't want to break friendship with both....I also want to change the attitude of "A"....