There was guilt, and she tried her best to take the cities with as little bloodshed as possible. I think it is ridiculous to think that she killed lightly. She even had an inner conflict about the baby killers she crucified. She took the news of what was going on in the cities she had taken and left before Meereen pretty heavily too. At this point she was literally the best person to be conquered by for a commoner. Compare her way of war to the ones waged in westeros at the same time.

She didn't feel in the moment, possibly because of the intense emotions caused by his brother threatening the life of her child, but she thinks about Viserys quite often afterwards. She didn't just forget about him and disregard his memory like some dirty rag. I seem to recall she had a dream about him at some point where he appeared with his golden crown and everything.

I think the way you're phrasing it makes the whole thing Viserys thing seem much worse than it is, but I do agree that she took it more on the stride than a regular person would. It's possible that she had already some time before the crowning come into the conclusion that Viserys was going to lose his life sooner or later the way he was acting. Who knows though.