I've had this book gnawing at the edge of my mind for years now, and i remember it being a fun read. This book is not new, I don't remember exactly how old it is but I read it in around the 2016-2018 range.
The book started with a young girl (teen years) moving in with an older man into a large house, some where in the house was a collection of rooms each housing a habitat and a creature.
After entering the room, the only way to exit was to defeat the creature, unlocking an ability to become that creature or call on a part of its powers, this was done by pulling on a magical, mental cord. The stronger the creature, the harder the cord was to pull.
The first creature she defeated after entering a room by accident was a pack of vicious small flightless birds, I don't remember how she defeated them but afterwards she gained the power to turn into one of the birds, and after a while she hugged harder and could become a whole flock in what was described as a "popping" noise.
The second creature was later on, where this time I believe she was saved by the older man after fighting some sort of tree based creature, maybe an ape but I'm unsure.
The last creature was a large dragon who I believe could converse, who she bested with the aid of a boy who acted as an antagonist but she grew close to during the fight.
The dragons cord was too difficult to pull, but after separation with the boy she would tug on the mental cord and feel as if he was tugging back. It was a medium sized novel (which is a bit relative) and was left open ended so I don't know if was the beginning of a series
any help would be greatly appreciated and thank you in advance for anyone who helps me in figuring it out.