As with any unfamiliar symptoms, I'd advise getting things checked out by a doctor.
However there are two symptoms which I've suffered (often simultaneously and for no obvious reasons) when my immune system has clearly been working at less than full efficiency. (Often when I've had a bad cold or similar). One is lumps in my armpits and the other has been lumps in my mouth (which sometimes become mouth ulcers before eventually disappearing).
So, while I repeat my suggestion that your mother should see a doctor (just to be on the safe side) I can tell her that I've had the same symptoms several times and I've not dropped dead yet!
;-)
Chris