I understand how hard it can be! My second child sleeps much like yours.
This is interesting to me because I think if my second was an only child he would be like this but because we can't stay home (taking older brother to pre-school, picking him up, then errands) He sleeps when he can. Now at 21m he does get predictable sleep most days because he just falls asleep when it's time for him. Possibly have a day where you just see how much and when she sleeps without any guiding on your part. Maybe her time of sleep and process of falling asleep is changing? I think 45min is pretty good for one nap, is that all naps then for all day? How much at night?

You might want to toy with contributing factors such as food allergies
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Here is a thread about an 8m old who wakes allot at night. Maybe some of the ideas might help.
http://www.attachmentparenting.org/f...ssy+baby+sleep

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Transitioning from nursing down to dad rocking to sleep

Thanks for your support and suggestions. I now am faced with a related but different problem. I have been nursing down my 6 month old daughter each night for bed and at every waking but I am exhausted and sometimes need a break from being the only one who can comfort her. My husband and I decided to try letting my husband help put her to sleep, after I nurse her. It is our first night trying this out and she has been screaming (while my husband holds her) for about a solid 25 minutes. This feels like CIO to me but I know that it's not because she is being cuddled and comforted by my husband. Just wanted to see if anyone else has had this experience and check in to see that I am not doing any damage to my daughter's attachment to me by doing this. This is a very hard process for all of us but if, in the end, my daughter is able to be comforted and put to sleep (and back to sleep) by either my husband OR I, then I will not feel as exhausted or as unable to go anywhere in the evening.

you say she's crying in arms w/your dh, but you also say that she fights sleep w/you. does she cry w/you that much?

No, she doesn't cry with me when I put her to sleep. I usually lay down to nurse her and then she falls alseep, no crying involved. When I said that she fights sleep with me, I only meant that if we are not at home, she doesn't want to fall asleep often because she gets distracted in different environments. Also when we are at home, she sometimes won't stay asleep for very long. She lets my husband put her down for naps (he rocks her to sleep) but doesn't want him at all at bedtime or during any of her night wakings.

I can definelty sympathise with you as my son who is now 8 months has also had sleep problems right from the get go. I think people just don't understand how frustrating it can be when your so sleep deprived and your baby just won't sleep. It becomes difficult to be the best parent you can be during the day when your just so tired all the time. My son actually slept on top of me for his first 4 months because that was the ONLY thing that worked. So it's been a long road for us but at this point I think we've finally mastered day time sleep although I still have the same problem you do during the night. My son wakes every few hour at noght and needs to be nursed back to sleep. But during the day he now takes 2 2hour naps. It was a long hard process but it was so worth it!. I don't know if this will work for you but this is what I did. First a very strict scheduale is a must, this ment skipping alot of play groups, day trips ect. in order to be home for nap time. Also I've discovered there are nap windows, times when my son will easily fall to sleep, if I miss the window I miss the whole 2 hour nap! The first nap was the easist to introduce ( my son didn't nap at all before this) it would occur within 2 hour of getting up. At first he'd fight it like crazy it would take me an hour sometimes to put him down for a 30 min nap. But I wouldn't give in, we'd do the same routine- put away toys, dim lights, shut the blinds, put on soft music and dance with him for a few minutes then go into the bedroom and basically stay there till he was alseep. No talking just soft wispers to calm him and no playing or interaction. He would fight it like crazy crying in my arms, I don't believe this is the same as crying it out because I'm holding him trying to comfort him. Eventually he'd always fall asleep though, you just have to be more stuborn then they are! The second nap happens 4 hours after the first. So if he's up a 7am then naps are at 9am and 1pm. It took a good month or two but now he falls asleep within minutes and sleeps for
2 sometimes even 3 hours at a time! Since he's been napping his whole personailty has changed, he's far more calm and predictable. I think the hardest part is sticking to the scheduale because it does leave you some what house bound. But now that our scheduale is well established we can break it every now and then without much harm done. Also I should mention that at the nap times my son doesn't really seem like he's tired, not fussy or anything and I think thats the key- put them to sleep before they're tired because once there in a tired state they seem to fight it and it becomes much more of a battle to get to sleep.
Sorry that was kinda long but hopefully that helps you out!