girl pushups will work. If she can't do a normal one. I dont know the real name for them. We just call them that cause in high school phys ed thats what they would do. a normal one as you know is toes and hands. Instead of being on the ground with your toes, girls use there knees so they arent pushing up as much of there body weight. It helps your shoulders, chest, and back so she should benefit from it. another way to do a girl push up is lean against a wall and do it. find her max amount then do three sets a night. 1st set is starting from her max amount of reps, subtract 2-3 for the next set, and 2-3 for the last set. if she is sore the next day, tell her not to do them until she isn't, or has little fatigue so the muscles can repair.