I assume she is contracted out of SERPS.
A few questions first:
When you say she 'takes home' £2600 pm is that after all deductions (tax, pension, NI)
When you refer to £14000, is that the annual pension? Can she get a lump sum as well or would taking a lump sum mean a smaller annual pension
Anyway, although you use the word 'offered', I can't see her being able to negotiate any more- that is the pension she will get if she retires now.
She can take a lump sum which she could use to help pay the mortgage over the next two years.
I'll come back after you've had a chance to answer my queries