@SilverSupreme That's an interesting line of thought, but something about it still bugs me. I think the trick here is that "Earnestness and loyalty to his crush" does not mean he'd have the same earnestness and loyalty to just anyone. Let's accept the hypothetical that Ushio is reacting to his honest declaration that he has strong feelings, doesn't expect them to be returned, but that he's just not interested in anyone else regardless; Ushio hears that and thinks "wow that sounds great, I wish I was that girl! maybe?"
Well if Ishizumi is so earnest and loyal, but is willing and able to give it up and date someone new, then was he really that earnest and loyal? Ushio's attraction to his loyalty to someone else seems like a contradiction. Irrational.
I think it's more likely that she's looking at his stats- Career, income, body. She hears he's not really looking to meet someone new, but his stats are good, so she is trying to get him interested in her anyways. If that's her motivation, then she doesn't care about earnestness and loyalty at all! She's actively ignoring his feelings, so she can get his bag. That's no basis for marriage!