As others have said, a bigger problem is the casual treatment of domestic violence. It's out of place in respect to tone, and depending on one's personal feelings, it's a very poor way to treat the problem of actual, real life abuse. (I make those two things separate distinctions because people feel differently about how horrible things portrayed in fiction ought to be treated.)
While a discussion on the inherent imbalances in a relationship with a not-insignificant age gap is certainly a worthwhile one to have, I think it's not a problem in the case brought up here.
(And yeah, 10 years is a fairly insignificant gap in the grand scheme of things, but context matters. An 18 year-old should obviously not be in a relationship with an 8 year-old. The difference between 18 and 28 is not nearly as significant as that, but it's still more significant than, say, 28 and 38.)