Just watch out. All she seems to do is sit around and eat bread. We're not married, I'm waiting to see if she puffs up.
She is supposed to do things in her bedroom. However, when you bought the "decorations" for your house, that bed got marked as owned by someone else. For whatever reason, she doesn't recognize her room as "hers" and so the only thing she ends up doing is sitting around and eating.
This will probably be patched in. It's funny, but the coming patch will probably "fix" Lydia sitting around and eating before it will fix some more serious balancing and stability issues.