hi Lisa
I've seen some of your other posts and am sorry to hear you are still having some sleep trouble. It all just seems so much worse when you are sleep deprived, so here's a hug coming your way.
I think there's a few different things in the mix here. Firstly, yes the short naps will cause overtiredness. But she is lengthening some naps, so she can do it. It seems that if she wakes she is unlikely to go back to sleep. So the thing to do is stop her waking in the first place. I would recommend giving w2s another go- bear in mind you need to be consistent and do it for
every nap for a good number of days before it may take effect. It's hard work but pays off if you can stick at it.
Also I think if she is used to falling asleep on the breast that will cause some problems too as she will need you to get back to sleep when she wakes at night. When she falls asleep at that last feed, have you tried waking her just before you put her into bed, so she goes down awake? It's amazing how easy it is for babies to learn sleep associations and how they can differentiate between naps and night sleep. My friend's lo will go down awake in his cot for all naps, sleep like a dream and if he wakes can put himself back to sleep. At night, it's a different story- he will only go to sleep on my friend's bed with her there, and then she transfers him asleep to his cot. If he wakes in the night he can't resettle and she has to take him in with her. What I'm trying to say is that maybe she has learnt that mummy will feed her back to sleep in the night when she wakes and that's why she's not settling.
I'm no expert on breastfeeding or props but will ask the other mods to have a look at your post and see if they can help
kathryn