YANBU but agree with Bruffin - you need to make time for your mum, that will then stop her wanting to speak to you all of the time and give you more time in the long run.
It might not. It might cause OP's mum to think 'See, she's had time to talk to me all along, she's just been difficult about it...' and lead to heightened demands for OP's time and attention, which in turn can lead to further tension and disappointment/guilt. (Speaking from experience here.)
not sure why OP can't find time for a 10 minute chat every so often
In my experience the problem isn't 10 minutes, it's an assumption on the other person's part of 'ah, she's finished work now', leading to further expectations being placed, and ending with the other person getting all disappointed when those expectations aren't met.
I acknowledge I'm basing these statements on my own experiences which don't apply to everyone, but I'm imagining that these are possible problems in the scenario OP is describing. Someone accused the OP of being judgey in mentioning that her mum hadn't been to uni. I don't think it's like that at all - different people have different working histories which tend to shape different expectations and assumptions about what work is, that's all. I think it genuinely can be hard for people who have worked in a different type of environment to understand the need for concentration and minimal interruptions when a person is studying or doing other concentration-heavy work. (I don't mean anyone on here btw, I'm speculating as to why this might be difficult for the OP's mum.)