Andrea:

Does the bike still fit you? I mean, frame size & standover height; saddle height, are you comfortable reaching for the handlebars? Can it still be adjusted to fit you now that you're grown? If so, it's probably still a good bike.

If not, then consider swapping it for a new ride...

Another thing to consider is how much it will cost you to repair or replace any worn-out parts. If more than a hundred bucks or so, then think about a new bike.

Tom