Sounds odd Scoobs. A settlement figure is the figure required to completely settle the account, all outstanding payments including any optional final payments and any interest and stuff that was part of the schedule she will have signed at the start of the agreement.
You're right to be suspicious when another two grand all of a sudden comes into play. The only thing I can think of apart from someone trying to lift your leg is that the current car is only worth £2500 and so negative equity is being re-financed. Check the true trade value of the current car and see if this could be the case.
Get your Girl to speak direct to her finance company and ensure that the settlement quoted is the settlement.
Challenge the salesperson about it, then the sales manager.
Hope this helps.
Jon
You gotta tie yourself to the mast my friend, and the storm will end.