Don't worry! They all get grey hair at the age of 45.

They should have a lot of time left in the game.
If you really want to make sure they stay around for a long time, praise them when they exercise, give them vitamins, fruits hand gel and try to keep the fridge full of food for when you close the game. I always try to get their health bars all the way up.
In this game, 60 is a long life for them but in the first generation they tend to go in their late 50's since we didn't get to buy them a lot of the things that help.
best of luck with them, I love the hairstyles!
As for how long a family will last, 7 years go by in the game in 24 hours of our time. They age by one year about every 3 and a half hours. You should have at least 2 more days with her or something if my calculations are correct.

Just remember that no matter how well we treat them, they all have their time to go.. so if she passes before the 2 days I predicted, don't blame yourself!