obviously he knows her better and probably believes she would get awkward so maybe its for the best. I wouldnt say he's putting you in the background, more like first if he's making other arrangements for his child in order to spend time with you. In an ideal world, your quite right, she should just deal with it, but it isnt and even when people have moved on, they still havent if u get my drift. Maybe u could have a word with her , woman to woman ?