Possible miscarriage or?

I'm actually asking this for a friend (seriously it really is.. I'm not just saying that)..so my friend has been trying to get pregnant for several years and has tried many different methods except IVF but she hasn't been able to get pregnant. Her doctor says she has unexplained infertility and nothing is wrong on her husband's side either. a few months ago after trying multiple rounds of Clomid she decided to take a break because she was mentally exhausted from trying so much. So she has been relaxing and enjoying life, well this month her period should arrive on 8/21 but since yesterday 8/17 she has been having severe cramping and she even got sick last night. She has had some brownish/red clots pass, there is no flow at all just the clots. Of course she thought possibly a miscarriage but besides the clots and the cramps the previous night she hasn't had any other symptoms. Has anyone else had anything like this before? Could she be having a miscarriage? or could it be implantation? Any advise or help would be great. She plans to go to the ER if it continues or the cramps return.