First, it's never okay for someone to demand that you change. When it comes to change, always listen to yourself and do what feels right to you. Second, if they've moved on, it's probably best that you try to move on, as well. At first, it might be hard to look past the feelings you had for this person, and they might feel so perfect for you that you get hung up on them. However, relationships end for a reason, and it's likely that there's someone better for you out there. Spend more time having fun with friends or family so you can start to move on.