Flagyl question?

My daughter just finished 7 weeks of Flagyl. We have suspected that it's the Flagyl that has been the cause of her feeling so immensely tired. How long would it take for her energy levels to return after discontinuing Flagyl. She's hoping to be able to bounce out of bed tomorrow, but I suspect it might take a week or so. 

My daughter was on Flagyl for suspected C Diff about 10 days - horribly exhausted, etc - but bounced back within just a few days.