Has she always preferred a longer A to BT? That might be the key here, figuring out which way she likes it. If that's the case, she may have been slightly UT, but that's still 5hrs A. I'm betting as she's been a little off colour that she may have been a little OT, but unfortunately we won't be able to figure that out until she's completely well again and settles into a more stable routine.
Up to you about the nap hun, personally I would push it as I said earlier, she might refuse a nap later on leaving you with a very long A to bed. Trust your mummy instincts, you know her best x