WBAC are not the most generous of companies but they do quick, no-hassle sales. You could maybe get more for it on AT, but would have to deal with timewasters and scammers for potentially weeks. Skip going on those weekend rides because someone will “definitely” be round to see it at 9am but not even have the courtesy to tell you they’re not coming.
Offer if you want, but she may just want a quick sale and have it out of the way.
Edit: glass’s trade values for that car:
Part-exchange Price:
Excellent condition:
£6780
Average condition:
£6320
Below average condition:
£5550
Hard to compare with AT as all but one advert (which is for a CatD damaged/repaired one) are trade sellers, and they’ll always charge more. That colour sounds horrible too.