It sounds like a fertility issue with your Serama eggs. How old are they? From what I've read about Seramas, they're super hard to hatch since they're so small. As far as the LF eggs, I dunno. You could have just made a bad pick on those and they were infertile too.
What are her brooding habits like? Does she get up often or take long breaks? Anything weird? I have a hard time believing there's something physically wrong with her. I have a frazzled Cochin hen (she got a double dose of the frizzle gene, so stays semi bald most of the time) who sits on eggs and hatches chicks. She's broody right now, if her nekkid butt can incubate eggs, I don't see why your little Serama couldn't...