Not sure what options you have other than telling her and it gets repaired or you get the watch back and she’s in the same position as she was before it got sent away. Or you pay for the repair as a Mother’s Day present!!
Sounds like it has been worn quite heavy if it needs a new case.
Previously I have found Rolex quite good when it comes to repairs outside of warranty. My mums Daytona was a year past it’s 2 year warranty period when the watch suddenly stopped working. Rolex, despite the multiple marks on the watch, repaired for free…although it didn’t need a new crystal or case as in the case of your mothers watch.
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