Oh! And was she transported in her own body or did she reincarnate into someone else, like a villainess?
I found this one as an Unlimited book, but there's no description:
Reincarnated Into A Character From A Novel I Read
https://www.amazon.com/Reincarnated-Into-Character-Novel-Read-ebook/dp/B0B6HFPYT4/
Bryan's Dog by Edmund O. Scholefield? (1967)
Bryan Cole, a poor Alabama farm boy, acquires a German pointer pup (Lady) which grows into a champion.
Keepers of the Hidden Ways by Joel Rosenberg. The main character is a college fencer, his family has used portals to travel between worlds for generations.
There’s a book called My Little Dinosaur published in 1971, but I’m unsure if there’s a museum and the main character seems to be a boy. Has a light blue cover.
https://www.amazon.com/Little-Dinosaur-Golden-Book-571/dp/0307020592
Any chance it's "Happy New Year, Darling" by Margaret St. George ?
The Beast by R.L. Stine? It’s not part of the Goosebump series: https://www.amazon.com/dp/B00DX7JDC8/ref=dp-kindle-redirect?_encoding=UTF8&btkr=1 + https://www.amazon.com/Beast-No-2-R-L-Stine/dp/067152951X/ref=sr_1_2?crid=2RDHNP6V8M7N2&dchild=1&keywords=the+beast+2+rl+stine&qid=1635125065&sprefix=The+beast+2+rl%2Cdigital-text%2C176&sr=8-2
house rules by jodi picoult? there are multiple covers but this one matches your description.
i dont remember the whole book but he has a bitch brother who calls him names and is into math stuff
Could it be Island of The Dolls by Jeremy Bates? I’ve not read it, but know that people decorate the area with dolls. Hoping you find, sounds good!