What happens next?

How to deal with a friend who constantly talks about her boyfriend
Be a good listener.
Though you may find it difficult to pay attention to what your friend has to say about her boyfriend on a constant basis, you should still strive to be a good friend and be a good listener. Being a good listener does not mean sitting there passively and nodding at everything she says.
Instead, you should try to be an active listener who asks questions and engages with your friend. This will allow you to feel part of the conversation and make it feel less one-sided.