If it's just running and gym she does, basically any watch will work capability-wise. Some specific lines have extra features geared towards other sports like diving, golf, etc. Other than that it will really come down to budget and aesthetic preferences. I would suggest just going on the website and having a look. The size of each model is also listed which is probably relevant if she is petite - some of them are pretty chunky. Forerunner and Vívoactive lines are both pretty suitable I would think.