Wait what really? Hmm tempted to do this but Nova flat out told me she didn't like Gob like that so she may just be after the money.....Oh I know I'll kill Nova too! 
It's never explicitly said, but it appears to be the case from their dialogue. Nova no longer works, but she talks to Gob to let him know that she "arranged time" for them. There is another conversation where Gob let's Nova know that he got a bottle of wine for her that makes her "uninhibited", she calls him Gobbie afterward, and he tells her that he would do anything for her. The sign for Moriarty's Saloon is also crossed out to say Gob's Saloon instead.
Moriarty pretty much has Nova working because she owes him caps (which is more explicitly spelled out in the Game Guide), and Gob is basically his slave, so I think killing Moriarty is the right thing to do; I usually mez him (while hidden), and let Jericho kill him.