I think the NW sounds developmental tbh. As you said, if she's learning her new skills quickly it won't be long until she's walking. Of course I understand what you mean! We had it here too.. It's like they want to keep doing their new skill over and over don't they?! You'd think it'll tire them out more
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That 45mins nap might be OT today dyt? Considering she normally will sleep 1hr 15mins after a 8.15 wu. Either that or there is definitely some discomfort going on that stopped her going to the next sleep cycle. Could she have been hungry at all? Sorry, just read that you fed her solids, so scrap that.
If she woke at 12.45pm today, I would try for another nap at 3.30 perhaps? Otherwise that's going to be a very long A to bed. It's a hard one to judge as mine could do a full A on 45mins sleep some prefer a bit less after a short nap. I have a feeling yours is more like mine.
She's 9mo old now isn't she? Mine was doing 4hrs A in the morning about that time. Do you want to try 3hrs 45mins A tomorrow and see if that works? It might not though. I think you'll have to try and find the right A for her in the morning to get the longer nap, then if she does refuse the later shorter pm nap, then you could just do EBT. I know you originally wanted it to be the other way round but I think she might be preferring this way!
In order to get to one nap, you would ideally need at least 5hrs A in the morning to get a reasonable length nap, then it's not too long to BT. The problem is, the more you push out the morning A the more chance there is of OT settling in and thus making BT/NW worse. I really, really don't think you're quite there yet, but she probably will transition to one nap earlier than most lo's.
I think if we concentrate on getting that first A right to get a longer first nap, it will make the eventual transition to one nap easier for you both in the long run. She really needs to learn to take longer naps first.
D you have a wind down routine before nap time? It might be an idea to extend that slightly considering she's so mobile and things are obviously changing so much for her at the moment. For example, now my DD knows nap time is after lunch as it's the same every day. We then change her nappy, read a story then it's in bed. I had to start doing a longer wind down as she was too busy charging around the place and never gave me any sleepy signals either!
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now when we are reading our story, she automatically starts rubbing her eyes knowing sleep time is coming.
Tomorrow morning I would try the 3hrs 45mins A and do w2s at the 30mims point to see if that helps lengthen the nap. If not, I would increase it to. 4 hrs the next day and hold it for around a week and work on the w2s to lengthen the nap. I really doubt she'd need much more than 4hrs first thing to get a long nap in, but I guess we'll see.
9mo was a really tricky time for us too, so you're not alone.