The whole Fred going to get sugar thingy. And then the next day the sister shows up and they call a clinic. Please tell me what transpired there thanks.
shareWasn't she going through her cycle? Didn't you see her using her fingers to count?
share(SPOILERS)
That was very confusing to me too. (Especially since the long focus on the sugar dispenser a bit further on almost seemed to suggest they hadn't really been out of sugar and the whole idea of needing sugar was being used by someone as a pretext of some sort.)
But, anyway, it seems that Fred was realizing while at the store that she had missed her period and might be pregnant.
She then picks up some item (not shown, but presumably a pregnancy test) and slips quickly into a rest room (to use the test, presumably).
Her "burn out" afterwards presumably results from the turmoil brought on by the discovery that she's pregnant with Laurence's child right at the time when the two of them are trying to sort out all of the issues related to his sex change.
There's definitely a reveal toward the end of the film that there had been a pregnancy and she had decided to terminate it.