Is the pain at the top of the bicep? If so, it is likely the tendon that the tendon that connects the bicep to the shoulder is injured. Sounds like a strain or sprain.
Generally, you should rest the arm (i.e., not pitch for a week or so).
You can ice it, which will bring the swelling down and relieve the discomfort, but icing doesn't magically heal the arm. The only thing that will heal the arm is rest.
Don't ice the arm, and then go pitch some more. You could end up with permanent damage to the arm.
If when she tries to flex the bicep muscle and it twists at the top and bottom, DO NOT CONTINUE PITCHING. You may have a torn bicep ligamate and you should take it very seriously.
Get to your MD and get a referral to an Ortho surgeon, do not leave until you get that referral because an X-ray will show nothing.