Hi
First up, big hugs. Sounds like you're having a hard time. Hopefully, between us all we can help.
10 hours sleep is great!!! WOW! DS has sttn once in 9 1/2 months (that was only 7 hours!)...so it's not all bad. Am I right in thinking that nights are okay except for the first few hours where LO is waking within 10 mins of shh patt to sleep? Wakes from naps at 45 mins everytime? When LO wakes, is she happy or crying? Tired and needing more sleep or ready to be up and playing? If the latter (up and ready for A time), is she happy and awake for the rest of the A time? I think you mentioned that she's not fussy after a short nap? Feeding well etc?
How do you get LO to sleep with ssh patt exactly? Swaddled? Put in cot awake and patted into sleep or shh patted until she's close to sleep?
Just trying to get a full picture of what is happening. Your nights seem really really good aside from the first hell hours (just my opinion) so reluctant to offer advice that may upset that without understanding what happens during the day and how LO is generally.
Some LOs do have really tough patches in the evenings. Sanaya asked about reflux & colic - these can hit hard in the evenings especially so really worth investigating that. Some babies can just be more upset in the evenings and it remains a mystery as to why.
For now, stick close to your baby and offer loads of reassurance. The CIO is scary for a little one as you are their whole world, so might be good to reassure that you are there and not going anywhere, won't do it again and always will be there for her. I believe building up some more reassurance will pay off.
A couple of links that might help:
http://babywhispererforums.com/index.php?topic=85134.0 - Typical amounts of day and night-time sleep
http://babywhispererforums.com/index.php?topic=10385.15 - Sample EASY routines for 3 - 6 months (take a look through for similar aged LOs for ideas).
TBH, I think your LO may nap longer after a slight increase in A time as she isn't fussy after a short nap. Check out the sleep guide and example routines and see what you think.
Hugs
Charlotte