A very appealing portrait but the first thing that hit me was the background.
I like your composition the way you have positioned your mum off-centre sideways on looking over her shoulder. She has a lovely appealing look that you have managed to capture in a sort of candid unexpected way which really adds to its overall impact.
I see from your comments received that the background has caused mixed reactions. Unfortunately for me it dominates in an intrusive sort of way that is effectively competing for my attention and drawing me away from your mum. It is very soft and enables you to isolate your subject but for me it is just too soft. I'm thinking its a floral arch? If so, I think there is a strong argument to use a smaller aperture to bring more detail out of the background showing us that your mum is in a lovely floral setting. As it is, it is so soft that the background confuses and distracts but as you can see, for others it appeals.
A luvely mum! The background really makes me dizzy here. I think the saturated colors and contrast in the background draws me right past the subject, who appears to have less contrast and is more neutral in color. Perhaps centering the subject would have caused the background to frame the subject leading to a better composition.