I third Bujold's "Cordelia's Honor" (aka "Shards of Honor" + "Barrayar").
Bujold's "Falling Free" and "Ethan of Athos" are standalone books in the same world, with some romance, although it's not as central to the plot in either of those. (In "Ethon of Athos" the romantic couple are both men, in case that's relevant.)
Some of Lee & Miller's Liaden books are also romances. I recommend starting with "Local Custom". (Warning: Many of their books have romance as an important part of the story, but not all of them have the HAE/HFN (happy ever after/happy for now) ending that's central to the romance genre. "Local Custom" does.)
I have a feeling I should know of more SF with romance, but I can't think of any now. If she's also interested in fantasy, I'll have a lot more recommendations.
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"hahaha"
"guilty pleasure"
Sigh. I really wish romance wasn't seen as ridiculuos or something to feel ashamed of.
