Morgana nods toward Gwen, to prove her point, "Beautiful, is she not? That dress looks lovely on her."

There is a big difference between the attention she gets at feasts, and having those around her notice the changes that went on. Particularly in the past couple of years. Morgana's always been Arthur's other side, the one to give him other opinions, and even that's been mostly replaced by Merlin.

If Arthur pays too much attention to the resplendent Gwen, he may turn back to see Morgana's disappeared back to Morgause's side. Morgause isn't paying the least bit of attention to the proceedings.