Nope they got together before the hundred day jump."not together"? I think you mean "together".
There was 100 day jump. If you're not with Liza, she'll go back to Brody. He may be a piece of shit, but so is the MC for dumping her.
She would have to be a real moron to accept him back even after a hundred days.
Lets pretend to it was with 100 days. To go from screwing her and relationship to none with no explanation is just fucked up.