If you don’t call, what you’re feeling may not actually be guilt. A lot of the time it’s grief for the relationship you never had, or empathy for a confused elderly person. You can hold empathy for her situation without being directly involved.

And if you feel like you need to do something to settle your own conscience, a phone call isn’t the only option. Calls can be high pressure because they require you to respond in real time and can easily turn into something emotionally draining.

A lower;stress alternative would be something like a short message or card, for example:
‘I heard about your injury. I hope you’re staying comfortable and that your recovery goes smoothly.’

That kind of response acknowledges her as a person and recognizes what’s happening, which often eases that internal pressure without opening the door to a long or stressful interaction.
And about the fear that this sets a precedent: that’s a valid concern. If you do choose to call, it helps to go in with a clear boundary already set, like a time limit and a simple script
‘I only have a few minutes, but I wanted to call and say I’m sorry to hear about your injury. I hope you’re getting good care and healing well."

If she’s confused or doesn’t remember the past clearly, you don’t need to bring it up, but you also don’t have to pretend everything was or is fine. You can keep it grounded in the present moment.