Exactly Willow's problem, as well as her single-minded pursuit of trying to salvage a situation that simply can't be salvaged. I, personally, think Willow's having a very human reaction.

Her reaction (save who you love even if it costs lives), honestly, isn't much different than Buffy's vis a vis Angelus and Xander's with both Willow and Anya. Since it eventually worked out for both Buffy and Xander, Willow has every right to expect that it'll work the same for her.