Suggest Remedy For Petechiae In Ankles & Feet

my 14 year old white female daughter is a travel soccer player and also plays for school. This week she has developed petechiae on her distal ankles and dorsal surface of feet. Slight calf pain right side. has played for years now. this past week has been hard practice and games. Plays the full game. I dont think her socks are too tight. No other bruising, nosebleeds, etc. What could this be?