The transformation should be slow and painful.
At first she will become less and less human in size, her spine strengthening to carry the constantly increasing weight, soon becoming even less feminine than she already isn't.
The spine will extend and produce a tail, the vertebrae showing along the line of her back, her fingers will turn into claws, making it hard to manipulate with.
And this is only the beginning...
I approve this request on basis of being a faithful player for so long and knowing that Tom here, would play that creature authentically.
Assigning Atherin for this one, he's planning to do draconic events already.