Zaid Alsalami, Shaykh Dr Zaid Alsalami is an Iraqi born scholar, raised in Australia. He obtained a BA from Al-Mustafa University, Qom, and an MA from the Islamic College in London. He also obtained a PhD from... Answered 2 months ago

Bismihi ta'ala

If this was accidental, and not in her control or on purpose, in that she was not "masturbating", then there is no sin and she does not need to pray for forgiveness. 

Of course, if she knows that doing certain things while exercising, or some kind of friction, etc, would sexually arouse her and lead her to reaching climax, then she must avoid that. 

And Allah knows best.