hi madallie
I started typing a reply to you on that other thread but I'll put it here instead, though the nap routine you've posted here is a wee bit different?
First of all please don't think you are doing anything wrong! My DS used to be exactly the same, every single day was different & it was incredibly hard to get a routine down so I know where you are coming from. But with hindsight I know that no matter what you do there will always be slight variation (because of activities, because they are more tired some days than others etc). I also learned that my worst enemy was myself - I'd try something for a couple of days, got a different result each day so decided it wasn't working & would try something else. Meanwhile poor DS's bodyclock must've been so confused, there's no wonder we didn't settle on a routine. What I finally learned is that whatever I did, I needed to do it for several weeks consistently, before judging whether it was working or not. I needed to give my DS time to adjust to it, & thats exactly what I wasn't doing.
So my first advice is to be consistent. If you want to establish a routine one way to get it going is to wake her at the same time each day eg 7am, so you are always starting from the same point. It can be tempting to let them sleep, but if they wake at 6am one day & 7.30am the next, they will need to nap at totally different times. Once routine is established, you can start to be more flexible with it, but short term, it really does help things to fall into place.
I would then stick with the same naptime each & every day, give or take 15mins if she is extra sleepy. This way you are giving her a consistent routine & this will allow her bodyclock to get used to it.
Some things I do want to ask are:
Is your DD happy & content during the day??? Does she settle well at bedtime? Generally STTN with no night wakings? Are her naps typically 1h 15-1.5hrs or more often than not 40mins?
As really & honestly, the napping routine you are aiming for looks ok to me. If she having between 2-3hrs of daytime sleep most days & going to sleep at 7pm wakening between 6-6.30am that really is pretty good going. I really don't think you need to change anything, unless her naps are consistently just 40mins or she starts consistently waking before 6am.
If she does start waking earlier more regularly, you could try cutting her morning nap a touch shorter, by 5mins every 3 days until the EW stops. I see you already tried a 45min nap but it led to a short 2nd nap too. When you cut the first nap shorter, you will need to bring the 2nd nap earlier to compensate. As if she normally naps 1h 15mins & stays awake 3hrs before needing another nap, if you suddenly wake her after 45mins she probably won't manage staying awake 3hrs as usual, she might need to nap again after 2.5hrs, make sense?
HTH.x