Well, according to Letho, Yennefer seduced Auckes when she was together with the witchers from the Viper school. You can argue she she had lost her memory and didn't remember Geralt, but the same can be said about Geralt. The first time Geralt remembers Yennefer is during the interrogation with Roche, which happens after he had sex with Triss. (temerian camp) The elven bath scene is the player's choice, so it's not canon. So I don't see your point why Yennefer has the right feel betrayed by Geralt. By Triss? Yes, she obviously abused Geralt's lost memory. But Geralt just didn't know about Yennefer until his memories returned.
And if I remember she did it on purpose, no? Oh, come on! Geralt didn't know about Yenn but Triss!!! That's a whole different situation. And that's the reason why Geralt is looking for her. He can told her that he lost his memory and Triss used this. Yenn has the right because she didn't know about Geralt lost memory and she simply know that her man and her best friend are together. Isn't this enough?