Is there anything my mum can do to increase her benefits income?

Hi guys, I think I know the answer to this (the answer being no), but worth checking just in case anyone knows something I don't.

My 60 year old mum receives ~£400 per month from an old DC pension pot that she took a few years ago. Unfortunately, due to ill health she is now unable to work, and has just been approved for PIP as well as the LCWRA portion of UC.

The frustration I have is that, despite it not being her choice to stop working, the money she gets from her pension is subtracted from her UC payments, and as she's under the tax free threshold, she's no better off than if she didn't receive the pension (in fact, she's technically worse off because it's a DC pension, so her pension pot is decreasing each month for no gain).

Is there anything she can do to see any of the income from this pension? Or otherwise is there often a way to stop the pension payments temporarily? I've tried to look this up but not having much luck. Thanks.