Bro, first of all, wrong choice of words - obsession is not a good word to use.
Secondly, as you said, when she goes to her home, she doesn't come back, that's but natural, that's the place she's grown up in, there's a comfort level attached. If you guys were giving her that homely treatment, I see no point why she'd not show interest. I've seen women loving the in-laws equally where they are treated nice and with respect.
But since you are the husband, take the onus of discussing this with your wife, AS HER HUSBAND AND NOT AS YOUR MOM'S SON and try to understand what's lacking. I am sure you'll figure it out. :)