My mom was riding her bike, and the pedal got stuck (it's an old bike). She pressed down hard on the pedal with the arch of her foot. This was Thursday. It didn't hurt when she did it, but Sunday, she had a throbbing pain in the arch (the mid-section) of her foot. Being on it made it worse. Now, the pain is spreading to her heel - she said the pain moves, which leads me to believe it's not a break, but maybe a pulled muscle. But, it's been hurting for days, and doesn't get better. It's not swollen, not discolored. She doesn't want to go to the doctor. She's afraid she'll have to see a surgeon, and doesn't think it's worth it. If it's sprained (can you even sprain that part of your foot?) she thinks there is nothing to be done for it. She has injured this foot before, but she heard something pop then, and it was twisted. Not so this time. Is it possible this pain isn't related to the bike incident at all? Will an X-ray from her regular doctor be able to detect what's wrong for sure?

Sorry to hear about your moms foot. An x-ray can show a break or other problems of bones. The best thing your mom could do is go to a specialist of the foot an orthopaedic surgeon or a podiatrist. They can examin the foot and run other tests if necessary they will be able to figure out the problem if her primary doctor couldn't offer her to much help or relief.
Hope this helps and she is feeling better soon!