I don't know. If Lanfear just had an angreal to boost her strength, wouldn't it have made more sense to wish for a sa'angreal to get real power. Even Alivia is stronger with her angreal than Lanfear was.

Besides that, in the end of TFoH, Lanfear uses the angreal Moiraine left at the doorway ter'angreal. Can you use two angreal ad the same time to have more Power?

I also think that the idea with a beauty ter'angreal is flawed. Normally beauty is in the eye of the beholder, some men prefer e.g. blond women, others dark-haired women. Therefore to wish to be the most beautiful woman to all people seems impossible. Or it must be a ter'angreal similar to the Crystal Throne, which basically Compels others to believe that Lanfear is the most beautiful woman. But since RJ said, that Semirhage could even counter the Crystal Thrones effect, I think at least the other Forsaken had also figured out, why Lanfear seems so beautiful to them and commented that they countered this effect.