Thanks both Sari and Layla. I also agree that she may be starting to drop her nap, but isn't it strange with the thumb sucking too? I mean she literally went from sucking her thumb a LOT (not only for sleep but also when reading books, cuddling, etc) to basically not at all at the same time. And she went from napping a LOT to this not at all. Seems so odd to me but then again she's always done everything to extremes - for example, she didn't walk until 14.5 months but once she did she walked all the way down the hall at once. And she didn't talk really at all until 21 months but now she's talking a TON.
As for today, she didn't end up sleeping in the car until on the way home from dinner. So she passed out cold (no thumb) at like 7:50 and woke briefly when we got home just after 8 when I changed her diaper and put on her PJs but then right back out.
I WISH she would fall asleep for her nap with me and/or DH - actually think that would be nice. But then she just thinks it's play time and jumps around. Grr.
Will just keep trying. If she really is dropping her nap, how long until you think she starts tacking that onto her night sleep? If she falls alseep so easily in the car does that mean she really does still need the nap? Not that I can force her to get it...