Hi welcome to HCM
Your daughter is regular in gym , swelling in 
biceps and discoloration  is somtimes  natural  , due to  over stressing of muscles with chin-ups . 
Over exerting always harms  .
 But dear there is nothing to worry . Our body heals on its own , due to self healing process  in our system  .   
Give her hot pack application on  swollen part .
after applying an anlgesic ointment .
Always remember, In case of any advice, please see your doctor / professional
Hope this helps solves your query .Take care .All the best .Get well soon
Take 
Homeopathic  Ledum  30 / 2 doses /  half hourly  for immidiate relief 
 Arnica 30  / 2 doses a day  / half hourly  . 3 days 
 Take Rest  ,till  amlioration .
Always remember, In case of any  persistant swolling , bruise/discoloration, please see your doctor / professional
Hope this helps solves your query .Take care .All the best .Get well soon
Don't hesitate to come back in case of any further query .