I have on old therapist who I've kept up with for 30 years now (God, I'm getting old). We touch base a couple times a year still. He's never moved locations, so it wasn't like I had to work to find him, but I think it would probably be okay to drop her an email with an update. You might preface it with a willingness to understand if she would prefer you no longer maintained contact (I'm assuming you could respect that if that was her preference?).