That was beautiful. Part of me really wants to see this continue and get its happy ending, but a part of me is also very content with where and how things were wrapped up. Also, not gonna lie, Mama willing to "sacrifice" itself so willingly made me tear up a bit. Straight-up MVP there.
As an aside, the whole mask thing, especially after reading the comments, brought some unpleasant memories from my first time playing Metro 2033.