welcome to cs! im sure youll get plenty of advice...just give it a day or so.
to be able to help you better, wed need to know how serious you mum is about her coffee and most importantly if she already has a grinder. buying her a $400 machine that she will use to make coffee with pre-ground supermarket coffee really is a waste of your money.
if shes using a plunger or stovetop already, then spend your $400 on a good grinder and her coffee will be hugely improved...then you can buy her a machine next year. :)
if she already has a grinder, then I would consider a good second hand espresso machine like a Silvia, they often go for about $500. this is much better value than a Breville, but you may not have time to find one before christmas.