Don't worry about it!
My girlfriend and I are the same age (36). She has been out of her residency (radiology) for 5 years. This fall, I'll be an MS1. On the serious upside, it is really nice being with someone who has "been there, done that". They already know that you won't have much extra time for the next few years, and you won't have to hear "You just don't spend as much time with me as you used to!"
On the downside (if there is one), there is the potential to feed on each other's obsessive, type-A personalities.