After reading the SWH addition-- it sounds as if possibly she is, as you already suspect, hiding any physical complaints from her husband. She may be telling you these things, asking you "Is it normal to just keep pain secret?" because her husband's attitude is, over time, making her unsure of what "normal" is any more. If the husband is unsupportive to the point of calling her names when she expresses pain, then I agree with your assessment that she likely is hiding her own pain so he won't be angry with her or think she's weak and a "wuss."
I think she asked you the question because she is frightened at being in pain but even more frightened to tell her husband or go to a doctor (possibly she fears her husband seeing the doctor's statement on their insurance records). She might have been seeking, from you, some confirmation that it's OK for her to keep pain secret. Or conversely, she might have been hoping -- without even realizing she was hoping it -- that you would say, "No, honey, it is not normal or OK to be in pain and let's get you on the phone to make an appointment right now...."
You can't read her mind but it sounds as if she might be cowed by a husband who--at best--is unsympathetic, and at worst, sounds immature, if he calls her childish names. You said he complains about every little thing. She may not want to be like that, so she hides every little thing -- and some big things too, like a possibly sprained ankle. He might have made being sick his "thing" to the point that he expects her never to complain (that's his hobby, not hers) and it's made her scared to voice any need for help.
OK, that's the armchair psychologist version. What matters is whether you feel you can talk to her and say, "It is not healthy to never see a doctor if you are in pain and don't know why. What most people do is find out what is going on. If your husband is not willing or able to go with you to a doctor, I will go with you if you need someone else along." I would not criticize the husband to her, beyond saying that if he can't make it to the doctor's with her, you're available.