My mom is going for a bone scan where they inject dye into the vein, but now they want to do 2 dye scans in one day so the minister doesn't have to help her out with a hotel to spend the night - should she be getting 2 scans in one day or not?

IV contrast can have negative effects on someone with insufficient kidney function. If she is concerned she needs to speak with her doctor or with the Radiologist/radiology tech. Performing the scans. Here is a site I found that gives pretty good information regarding CT and MRI and other types of imaging.

http://www.radiologyinfo.org/en/info.cfm?pg=safety-contrast