View the original post on Musing.io
I am a woman, and I am very familiar with your question. Maybe you try to keep good relations with him, don't give hope that you like she's but make a happy condition when you are with the girl.
The special attention you give can make she think that you are in love with the girl, and don't do it. Make him feel good as your best friend.
And if the woman wants to express her feelings to you, then you answer honestly that you feel comfortable when she becomes your friend not as your lover.
Hopefully my answer can make you comfortable, have a nice day.