If she has the ability to extend her hip (test by lying on back, bring the other knee to chest whilst keeping the ‘bad’ leg flat) I would put up with it for as long as possible. If she can’t do that it’s probably worth getting done – you need to extend your leg to walk, if your hip doesn’t do it your low back will – cue early wear & tear in the lumbar spine, hips can be replaced, spines can’t.