I think you need to decide on A times, and stick to them for a good week for things to improve. I think that 3.5 followed by 4 sounds pretty good for this age, if not a little bit on the long side, bit you can always put down early if tired signs are shown earlier.
Re the pregnant thing, I know that feeling. If it helps you, will you lo fall asleep with you in your bed? Then you could take your afternoon nap together. I know this is not exactly BW, and you probably shouldn't do it Every Day, but it has certainly helped me cope with the first trimester tiredness and a lo who is not too keen to nap right now.
If your lo is happy, then maybe, just maybe, she isn't overtired. My lo consistently does 13 hours per day or less, and is only a few weeks older than your lo. If she is happy, and healthy, and coping with the amount of sleep she is getting, then try not to stress about it.
9-10 months is a tough time for sleep due to so many developmental miletsones. We have some issues with this ourselves. I often have to do wi/pd/wo to encourage Zara to go to sleep. If you choose a method of telling/helping your lo to go to sleep, make sure you are super consistant with this also, and with winddown routines, I think it makes a huge difference at this age.