What should a 18 year old girl do to loose belly fat and to tone her arms a little?

Hey this isn’t advice for me but for my girlfriend. She is 18 and weights 180lbs and she wants to loose some weight but still keep her figure with the kinda big thighs but she wants to loose her belly fat and tone her arms. What would she need to do when it comes to exercise and diet and all that? Thanks for any help