UTM could have been avoided

so in chapter 54 rhys tells feyre that if she had stayed with tamlin and broken the curse by telling him she loved him, amarantha would have killed her. that's why he tried to scare feyre and tamlin and wanted tamlin to send feyre away. sure, plausible. but then utm came and feyre made the deal with amarantha to break the curse...shouldn't he have realized that amarantha would kill feyre anyway? rhys also kept saying how he knew feyre would be their only hope to free them all and that she only had to master the trials, but wtf did he think would happen after that? and when amarantha actually killed feyre, he was like "nah don't worry all high lords are here and we can save you" as if that wouldn't have been an option in the first place? it drives me insane that feyre's whole trauma from utm literally could have been avoided. amarantha would have killed her in both scenarios and she could have been resurrected in both scenarios. why did rhys not realize that? am I missing something?