OMG Christine!! I'm soooo thrilled for you!!!!!
Yes Sophie can only sleep so many hours and it seems 12-12.5 is what she needs right now. (illness and teething might make it more) So now that you know that its much better.
These toddlers are TOTALLY different from babies in the sleep department. They sleep (actually pass out some times LOL!) when tired and play or fight going down when UT. Or they short nap/wake super early in the am b/c they've filled their sleep bucket for the night.
I have to look at Anna-Li and Jace's sleep soooooooooo differently! With Anna, my goal is for her to wake in the morn (its been 7:45 most days this week........... SOOOOOOOOOO nice!!!) and wear her self out until its nap time (We do set time at noon or 12:30 with a late wake up... we could do later but she goes to nursery/preschool two days a week and I want to keep her clock consistent) Then when she wakes I just let her wear herself out again until she's good and ready for bed. (typically 7-7:30 but can be as late as 8pm if we have a low activity day or she's just going strong) Most days she only gives me a hour or so nap. But she sleeps all the way through the night (unless ill) every single night and is pleasant in the morn. NOW if I let Jace (baby) wear himself out and pay no attention to A time he'd be BESIDE himself, with constant NW'ings and EW'ings! It would be terrible. They are so different (toddler vs baby sleep)
Its WONDERFUL that she lets you know when she's ready for bed. Anna does this as well. Its super great since she's not giving cue's at the moment. I'd rely on her when you start nearing the A time you know she's been good at, just keep asking her. That's just what you want. She knows when she's tired and needs a restie! Let her tell you!
When Anna starts looking tired and we are near nap time I ask her if she's ready for nap and 9X out of 10 she will say yes. But if she doesn't then I tell her in X amount of time (5-15 min's) we will be going to nap. Also with bedtime, when she looks/acts tired I ask her if she's ready for her milk. Again she almost always wants it and knows that means bedtime. If not I also give her X amount of time before we go to bed.
As she's waking later in the am, move her nap and bedtime out further until you are getting the wake up you want. I've moved Anna back a bit once I had Jace. I just needed more time in the morn to bf and get around before she needed me. So do what works for you. Also if you want a wee bit more time with her after work (once you get back) then just set her clock now for what you'd like. You might even like a 8pm bt with a 7am wake. That's ideal for a lot of working parents so you are able to spend a bit more time in the evenings with them, if that doesn't work for her you can always do a 7:30 bt... but if she's open to it (as she tolerates moving her day back) go for it if that's what you'd like.
I also wouldn't set your nap until you are getting the bt/wake up you are wanting. Just keep moving backwards first. Then when you are at your ideal set it and your DONE!!! You and DH can both enjoy a sleep in EVERY morning.
Oh one more thing, also give her a bit of time after wake up and naps to go back down. I never leave Anna to scream/cry or get angry. But once I started giving her time in the morn/after naps she would sing and play and soemtimes go back down again. Now she plays VERY happily in her crib for up to a hour (which is a God send to me now that I have 2) and once she starts screaming 'mama mama out, down, stuck, help, poopy diaper' (all the words she can think of to get out) I go to her right away. You'll know when she's over it and just go to her telling her of the great job she did.
Your beautiful Sophie is growing up mama!!