Would echo the advice to get it done ASAP presuming that your mum is still able to consent.
We were too late with my Nana and so had to go through the Court of Protection which is a hell of a lot more hassle as you need submissions from doctors, care providers etc and then once granted you have to give a yearly report of any money paid out to show that it's in line with how the person would have acted if they were still capable.