Hip replacements take 3 months to heal. She may have had bone cancer starting which might explain her visits to the cancer clinic Charles is using.

The "abdominal" was misdirection, but only slightly so if you think about the anterior approach. Made me think she was poisoned which now am sure she wasn't.

With a hip replacement you can't walk without aids, which would not be a good look for her, and one she'd rather not have us see, given her rel. young age.