My child wants to read books at 3am

I need some advice, my daughter is 20 months old. Since she was 2 months or so we’ve done pretty much the same bedtime routine. Bath, books, songs while I rock her to sleep. I genuinely loved rocking her to sleep, I know she would never be able to do sleep training because when she cries at that time it is completely inconsolable.

Thanksgiving night when we were about to start rocking she pointed to her bed and said “in”, we sang her songs and she fell asleep. We were in shock! I didn’t think it would happen again but it did all the way up to Monday night, she fell asleep in her crib perfectly fine, but around midnight she woke up crying. Now, when she cries late at night/early morning we always just put her in our bed (I know there will be a lot of disapproval but it worked for us and we don’t mind it because she wasn’t starting off falling asleep in our bed). When we put her in our bed she was wide awake saying “down” and crying, eventually we brought her down and she brought us into her room to read books. Would not stop getting books from the bookshelf, and would only get through a couple pages before she went back over for another one.

She eventually fell back asleep after many tears. The following night, she wouldn’t even go in her crib, just wanted to do the book thing all over again. Eventually said she wanted to go to “in” her crib and fell asleep. This happened the next couple nights but with no wake ups. However last night she woke up at 3am wanting to do the book thing until well after 4.

Some things to add: we read lots of books during the day, to the point during these wake ups I’m reading these books without even being able to see the words lol. We start bedtime around 8, and she’s always been soundly asleep anytime between 8:30 & 9pm, waking up around 8-9am. We’ve had a very slight routine change during the day, but it’s very minimal, I’m not sure if this is contributing? The last 2 nights after all the book reading she wants to fall asleep in our bed.

I don’t know what to do, she has always been a decent sleeper and I’m not very functional at 3am. Is it the slight routine change? Is there a 20 month sleep regression? Why the books? Is this a result of semi bed sharing?

Any advice or similar stories would be great!

TLDR: my 20 month old who use I used to rock to sleep, wanted to sleep in her own crib a week ago, but is now not wanting to go to bed. Roams around wanting books read instead.