Next time you feel MIL is probing just give vague answers. You really don't have anything to explain to her. I also wouldn't bad mouth H - even if she tries to pull something negative out of you about her son. This may backfire on you if you rant and rave about her little boy.
M:43 H:37 D14 (ours) D18 (mine) S22 (mine) S18 (his) S: 10/2004 Bomb: 2/15/05 In/out of home Living with OW #4 Talks of D for 2-1/2 years