I've been reading books to Baby_Gurl but wondering what items I can use to help boost her intelligence level faster?

Tomes, like will boost all stats, including intellect. If you weren't aware, you get them by turning in the amulets from Quentin's quests to the Mage. He'll most likely give you a shard though. You can also read the tomes to your pet like a normal book, but you only get one intellect from that. The common intellect boosters are boosts health and intellect by 1 boosts intellect by 1 boosts intellect by 1-3

There are others, rarer, and more expensive boosters that will give you intellect but off hand I can't remember them. I think the Loyalty Tome Totem from the Loyalty Box will give you 25 intellect.

These aren't really faster than books, but you'll hit a point where the books your pet hasn't read are more expensive than the boosters. You'll still need to read a book to your pet to get AP if you boost past the point where you would get one. Don't worry about boosting a lot of intellect at once- you'll get all the AP you're owed once you read a book.

Her int is already too high to profit from the Spindles games, but if she hasn't read the exclusive books yet from that game, its worth playing long enough to earn the points to buy them.

Get her a job and be sure to collect income everyday - there's a small chance of gaining stats every time you collect income including Int.

For Oracle quests and scratchcards, I can't remember if they give out int, but if they do, make sure she's the active pet.

Another booster worth mentioning is the You can buy it in Esther's shop for 225 Vesnali Coins if you have a stockpile of coins.

This is very informative. Thanks everyone.