Although I share your concerns about your mother's diet--she's lucky to have you to help her--what's immediately more important is helping her recover her function and mobility. In particular, I'm
wondering about her being on bedrest. Unless the pelvis is very unstable (in which case the surgeons usually operate to make it stable), most orthopedic surgeons and rehabilitation doctors recommend that the injured person start moving around as soon as possible. Older people lose strength quickly when they stay in bed. Mobilizing and physical therapy should be done carefully, of course, and with supervision, in order to prevent falls.
It's possible she's reluctant to move because people also have a lot of pain after a pelvic fracture. It might be worthwhile double-checking both her pain management and mobility plans with your mother's doctors.
Although a nutritious diet is always a good idea, in the short-term it probably won't make a huge difference to her recovery. This is assuming that your mother doesn't have a medical problem that's highly diet-sensitive. For example, congestive heart failure and chronic liver disease are two diseases for which reducing ones salt intake can improve symptoms over just a few days. Diabetes can also be affected short-term by ones diet.
One risk of focusing too much on her diet is that your good intentions might create tension between the two of you. Instead of lecturing or just flat-out changing her meals, try to understand what it is that keeps her eating her less-healthy diet. For example:
- Is she unconvinced that there's a connection between nutrition and health?
- Is she resistant to your input because it's a control issue? Older family members sometimes want to be left alone about their eating habits in order to feel respected.
- Does she feel like she doesn't have time or energy to cook better meals from scratch?
- Is she under the impression that healthy food is too expensive?
- Or maybe she finds that low-salt foods just taste too bland?
If you can hear each others concerns and opinions respectfully, you might find her less resistant to little starter steps -- fresh apple slices for a snack, a green salad with her canned dinner, or adding lemon to brighten the flavor of a low-sodium soup. With your mother's permission, you could also bring up your concerns regarding her diet to her primary care provider.