Argh I had just written out a post and DS pushed the reset button on my computer!!
Sounds like you are doing well so far, its all about judging them each day and night and every A time after.
I think you made the right call(s) when you put her back to sleep etc rather than going for a 2 nap day at that point in the day.
I think that a 2:45nap is pretty good actually at this point of the transition. She'll need to do some catching up for a while, when getting used to the single nap and longer A's. Then as Megan says they'll either shorten it themselves by just needing less sleep or you'll have to cap it so they dont wake UT in the night. (Just wait for an UT NW and then start capping if you have to)
While she can only manage 4ish hr A times it's ok to have the long nap, and then go with the flow for a while doing one nap and two nap days as the sleep needs cycle round. I started to think more about the total sleep my DS was getting over a period of a few days (and even the week as a whole) rather than the sleep needs of each day individually. (Although these definitely do count as well!)
Then as he was able to handle the longer A's his sleep needs started to level out and so did his routine and then he was consistently on one nap and handling it well.
Keep us posted...