Good luck bro. Wish you the best....but from what you've shared so far my gut tells me this won't play out well.
You say you hope it is a phase. Flipping the coin over. Us guys love going out and picking up random for no strings poon right? But when we get married we know that phase of our life should be over and is no longer regarded as acceptable.
So her doing the same thing is somehow acceptable or tolerable?
Best of luck...but I do feel your emotions here are blinding you from seeing the logic.