Barbara Villiers or Catherine de Braganza?

A portrait, without indication of the subject but given as "Circle of Peter Lely", is for sale at Bukowski's, 8 February 2015, with an estimate of 3,200 Euro and a current highest bid of 2,500 Euro. (UPDATE: it sold for 5040 Euro in the end) Looking at the picture, I don't see a lot of Lely (well, every decent English portrait of that time is influenced by Lely probably), but it seems that the sitter is Barbara Villiers, who was also depicted a few times by Lely (or Studio), like the below picture from the National Gallery in Washington.

With the Lely association clear from the sitter's identity, the question becomes who the artist may have been.

The portrait for sale here is much closer to one attributed to Remigius van Leemputten, from the Royal Collection. Well, it turns out that that one is a copy after Lely after all, so "Circle of Peter Lely" seems quite correct.

But are we certain of the sitter? The above seemed pretty conclusive to me, but then I encountered Lely's portrait of Catherine de Bragança. Very similar to the Villiers one by Leemputten, but not with just the same hairdo and necklace and backdrop as the one for sale, but also the exact same dress, and nearly the same position of the hands (with a simlilar piece of cloth between them), and so on. Also from the Royal Collection, by the way. The one for sale is not an exact copy, e.g. the background is closer to the Villiers one, and the white cloth behind the sitter also covers the top of the chair in the one for sale.

So we have something between these two, and with the extreme similarity between "Barbara Villiers" and "Catherina Braganza", I don't dare to say which one is really being portrayed here (are we absolutely certain that the Braganza portrait is not simply yet another Villiers one? The same necklace, the same pearl earring, the same hair, nearly the same face: the Villiers has more weight, but that may be due to age only: the Washington one is closer to the Braganza one). If I had to chose, I would say that it is Villiers...

The one for sale is not a Lely, but how close to him it may be is unclear. It certainly is an interesting painting, for a very reasonable price.