She is lucky to have you, and you are lucky to be the kind of person who cares. It reminds me of how Milo looks out for me when I am falling in love too fast. Although I am usually the one who wants to rush things. All you have to do is calmly explain to her how it looks from your point of view. Give her the best advice you can and then respect whatever decision she makes.
People get crazy when they're in love, be a friend.
Try and guide her, but don't force her to choose between you and him. Good Luck, Simon. Hey Mike, Go to a movie and pretend you are tired. It seems like you are on the right track, if you can get close as friends, then maybe you can be more, don't push it, don't blow the friendship, unless it's keeping you up nights. Plan a special night and make it verbally clear.