It was bad enough for her trying to compete with a memory, worse seeing a version of that memory come to life (and trying to compete with Mai herself, if only on an instinctive level)...but seeing this version pop up looking for all the world ready to come back and take him away from her for good? Aw, hell, naw. At least she doesn't live long enough to find out what Shouko ended up doing later in this second timeline.