discuss it. Wait for an evening after the kids are in bed. Just tell her you think it’s important for her to try. Brain storm ideas together and put it on a list (lunch with a girl friend, date night, exercise time, walking around a book store, etc).
Then put it on the calendar, once a week, once a month, whatever you want to do. I think she’ll find that she does enjoy a little me time and it might provide a little more balance. And if you try that and she doesn’t like it, maybe that’s just not going to be something she does regularly. Some people don’t enjoy or want me time.