I agree that the bird looks a great deal like a female Rose-breasted Grosbeak, but she was much too small to be a grosbeak. Additionally, the beak is much more like a Purple Finch. And finally, I sent the photographs to experts who confirmed it to be a Purple Finch.
Here is a normal female Purple Finch at our feeder:
And here is a female alongside a male Purple Finch photographed in the rain.
We saw Leuci for only three days and have not seen her in a week. I had rather hoped she might stay around.
Thanks for your guesses. You figured it out pretty quickly.