Have you done early bedtimes before? On a day with a 30min nap, I'd definitely be putting down earlier than normal BT.
I think the routines you posted above both look fine. I'd be tempted to make BT a little earlier on the one nap day. Most LOs don't do more than a 12-13hr day when they first switch to one nap. Even if she ends up waking at the same time, she will have gotten more sleep overall so the next day should go better, iyswim. Even on the 2 nap day, I wouldn't push BT much past 7pm with a 5:30 start.
If i do go with the set naps and she continues to only have 30-45 min all day, she will eventually tire out and sleep wont she? How long did your DS take to settle into set naps?
Yes, typically if you stick with set naps the OT will eventually break and she will sleep longer. My DS has been on a set nap pretty much since he started one nap. It was first at 11:30am, after a few months moved to 12pm, a couple months later it moved to 12:30pm and now it's been at 1pm for the last couple. I expect it to stay there for awhile and I'll end up cutting it shorter eventually to maintain a decent BT and good nights.
I did go back and forth between 2 and 1 nap days with both of my kids for a few weeks, maybe even a month until they settled in to one nap. With my DD, I even had to give her a 2 nap day if she got OT while teething until she was about 2 (she was late to one nap though, at 17mo). I suppose it could mess up their body clocks a bit, but I actually found it to be very helpful during that last part of the transition.
(((Hugs))), hang in there!