Get her a present
You know your mum well so you are the best person to know what she would like to have. It doesn’t need to be costly though as the main thing here is your present should be something she would always appreciate. If you are still at a loss as to what to buy specifically, you could buy her some of her favourite items – chocolate, flowers, wine, and so on, and put them together in a gift bag. Interestingly, there are mothers who would want everything in cash. Put some money in an envelope for her if that is what she wants.