Now is the time to be honest with yourself. You need to find out why she left. People usually complain about money/equity issues when they think the situation is so crappy that only money/equity can keep them in the situation. Was there a lot of scope creep?

Let me pose this hypothetical situation. You contract with this developer to create your web app before you have fully spec'd it out. But that's okay because you're using more of an agile approach. The developer gets on with her job of creating a basic prototype and you tackle issues as they arise. Things begin to change and you see want a few minor changes to the web app. The developer not being very assertive, says okay to most change requests. But 6 months in things have changed so much that the developer realizes that this project will be in perpetual beta. You are frustrated because the developer hasn't finished when she said she would. She's frustrated because she realizes just how extensive the web app is and that she underestimated the amount of work that would be involved (and with the feature creep there is even more work now to boot). Both of you are so far away from the original terms of the agreement that the whole thing leaves a sour taste in your mouth. She can walk. But you're left with the tab.

If this sounds like your situation, I know it won't make you feel any better, but it's a common story. I think what you need to do is offer the developer a way to save face while helping get you out of your current rut. Chances are she's not very proud of having bailed on the project, nor does she want bad word of mouth to spread. She was probably frustrated. Can you identify her frustrations and address them? If so, can you talk her into re-joining the team and giving her the 35% equity? Right now, you have 94% of a whole lot of nothing. If she doesn't want to re-join fully, ask her if she will help document the project and transition it to another developer for you. If she does this, you will give her the existing 6% equity in the company. If she flat out refuses to talk to you, keep your composure and be polite but let her know that under the circumstances you feel her monthly payments were more than acceptable compensation and she has no equity. If this happens, your money is gone and isn't worth pursuing. But I would contact a lawyer in order to sort out this non-documented partnership. You will want her to sign something because right now there are a whole bunch of ugly intellectual property ownership issues that you are at risk of down the road.