J.M.
I totally get it. I had that problem with my first, and now my second is in the same habit. My best advice is to try not to let it bother you. Plan your life, and if she's napping, she's napping, and if she's awake, she's awake. Sometimes you will have to wake her to go someplace, and sometimes you'll be late, but that is life at this point. If she falls asleep on the way to the grocery store, either you drive around for a while before going in, or you wake her, take her shopping, and try to get her down for another nap when you get home. I know it's really really hard to be laid back about it, but I realized the second time around that my stressing out about it did nothing to change the situation, but actually made me feel worse. As she gets older she'll sleep more and be more consistent, but her little body is changing so much at this point that there's no point in trying to get her to be more scheduled. Also, try to remember that just because she's awake it doesn't mean she needs all of your attention all the time. She can go in the swing or on the floor while you do some dishes, or fold laundry, or check your email or get dressed. That way, when she does sleep you can veg out watching bad TV or nap yourself. I hope this was helpful and not annoying : )