"Eva van Marle" is much too weak to be by her

Venduhuis de Eland, from the Netherlands, sells on 15 September (today!)  a double portrait by "Eva van Marle (active ca. 1650)", probably the wings of a triptych, estimated at 2,000 to 3,000 Euro. (More images and the estimate can be found at Lottisimo, but not on the website of the Venduehuis apparently?

This introduced me to Eva van Marle, one of the relatively few 17th century woman painters we know by name and have some work from. She only painted portraits (as far as we know), all of them ca. 1650. So far, this fits relatively well with the work for sale (although if she really only painted portraits, the central panel of the triptych has to have been made by someone else probably). But the quality of the works by her listed at e.g. the RKD is a lot higher than what is presented here, and no other indication of why this is attributed to her is given (signature? Family tradition? A name on the back of the panels?). Comparing the above detail, which shows a third rate painter, with the portraits which are definitely by her and show a very skilled hand, I doubt that the work for sale is by her, and consider the estimate to be way too high.

By the way, they charge a 30% buyer's fee, plus 2% online fee, which is really getting quite absurd (are auctions the only shops where you have to pay more when you buy online?). Why can't auctions simply let you pay whatever you offer, and deduct their costs and profit from what they give to the seller? It seems as if they are deliberately being difficult, which is offputting to many people (and then they wonder why not more people bid at auction probably).