A:AnswerSweatproof? Yes.
Waterproof? Somewhat. It can handle some moisture (such as getting wet while washing hands), but is not claimed to be waterproof, so should not be worn when swimming.
A:AnswerIt depends on her weight more than height.
I am 5'7" & 150 lbs (on a good day lol) and I bought a small. If she has "thicker" wrists I would go with a large.
A:AnswerIt will track steps without Bluetooth. But many other activities like biking, don't track correctly unless it can get location info from your phone via Bluetooth. Also, call and text alerts only work w Bluetooth on.
A:AnswerI have a Fitbit Alta and my sister and I have challenges all the time. You will need to use the app to setup or view these challenges and you will need to sync your fitbit everyday for your information to be accurate in the app. Unfortunately, it doesn't sync automatically (that I have noticed anyway).
A:AnswerNo, its not a phone. You dont have a contract to fulfill. You could possibly make a trade wth someone. Or sale your current fitbit toward purchase if an HR. Im sure there are used HR's out there, especially of those that have moved to Alta. Im one of those.