the shot

My sister is 14 and went on the shot(December 28th) to help soothe her periods. My mom did the research on it for her, which I feel my sister should have done herself, and told her it'll work for her. She has been spotting a lot since Wednesday and now she is bleeding a lot(she says it feels like she's peeing) and she says her blood is a lot brighter than usual. She also has cramps that feel different than her normal. She just wanted me to post this so she could know if this is normal and see what else other women have to say about it! Please let me know!