With the way it seems that the secret Romulan cabal has invaded Starfleet I'd imagine they could have made things difficult for her, or she just could be naturally self destructive and despite having opportunities present to her post Starfleet she either pissed them away or chose not to take them because they might not have seemed good enough in comparison to what she felt she was due...that kind of stuff happens all the time in real life so it's not hard to imagine here.