Pinkranger

It doesn't matter whether the joint account is the primary account. Simply HAVING a joint account is what matters. Some people submitted joint account info with close to 0 balances.
If you want to keep the bills account separate that's fine and not a problem. A lot of people do it that way to make sure people don't accidentally spend bill money.

You have met the requirements to file an I-129F petition. Presuming you handle the paperwork properly, there's no reason the petition would not be approved. I think the situation will be far different at the US Embassy in Manila.
Honestly, based on what you've said so far, I don't think her chances of getting another K1 are very good at this point. If you and her explain the situation with the first K1 truthfully then it will be painfully obvious to the consular officer that she used the first petitioner to better her financial position for herself and her family. The first petitioner's actions would seem to confirm that he found out about her ulterior motive. I wouldn't be at all surprised if the consulate's Fraud Prevention Unit gave him a call and asked about what happened.
The reality of the situation is that she would have followed through and married this guy if he had shown up at the airport, just so she could get a green card and some financial security. This is the precise scenario they suspect when they investigate a relationship for potential fraud. They are almost certainly going to suspect that she's using you as her backup plan.
My recommendation is to give this relationship plenty of time to develop. If you start the immigration process before you've had a chance to collect a massive amount of evidence of a solid relationship then I believe you are almost certain to be denied a visa.