Hi Zen,
I agree 100% with the way Bruce's analysis of your situation. You admit that you're a little passive so you kind of sat on the fence a little here, because you didn't want to insult her. When it comes to finances and the fact you just don't have it - she should understand. But give her a break since she has OCD. Next time you need to clearly say NO.
Since we're on the topic of NO, I would like t osay that many women do suffer the inability to simply say "NO". Why ? - because we're people pleasers, want people to like us and are afraid people may call us the B word. Oprah once did a whole show on this topic of people pleasing and how we do a diservice to ourselves all in quest of making others happy. Oprah herself admitted to having a huge problem with it, but she has since learned to be strong and say "NO". It will be a gift you give yourself to learn to be more assertive(not b-----) and say no when you need to. When you become better at it then you won't feel guilty about it and have to attach an apology like "oh SORRY I can't". Friends and family around you need to respect that you do have the right to refuse sometimes. So I encourage all people pleasers out there (LOL - to firmly say NO once in a while and don't feel guilty. No more fence sitting Zen - it hurts the butt LOL - just kidding