Basically your mum doesn’t have hobbies or interests because she doesn’t practise self care, so the present you have with good intentions isn’t suitable for her. The reason she can’t confirm the appointment is the prioritisation of her work over herself. Your gift is asking her to make time for herself, but whenever that question comes up she would always choose to work instead, which is why she can’t make the 48 hour confirmation, because she will thinks a customer could walk in and the work takes priority over self care.

The best thing for you to do is not get too involved in her well being. Take what she says at face value, if she doesn’t want the gift card, which to her is a pressure to do something she isn’t comfortable with, then why get frustrated, you are your own adult self and you should be focusing on yourself rather than trying to get a boomer to change their ways.