oh my, all this work going into Lin's Hydreigon while I have a feeling the battle itself won't be the biggest problem.
as a matter of fact:
Ame lost on purpose. Why?
Ame and Lin secretly are very best childhood friends. Their favourite pastime was ripping heads off of spiders, oh, it were happy times.
Their ways separated at some point, but given Lin's character as it is portrayed, she suffered severe emotional damage because of whatever happened after that.
When finally meeting again, Ame instantly senses that change within her.
Somewhere deep down resides old Lin, the happy, spider-head ripping Lin. That Lin doesn't like what she has become and of course is looking for a way out.
Lin has often thought about the time, the time when her world was still okay, and she remembered the joy she shared with Ame during said pastime.
Her innocent inner self never really understood the consequences, and the ruthless Lin that is visible to outsiders just doesn't care.
Inner Lin decides to send Ame a message, her last cry for help, which is interpreted poorly by outer Lin, as there would have been twelve Pokemon available as messengers instead.
She even raised her little Deino to become a Hydreigon, so she could have three chances in one to break free.
Knowing her way around the inner workings of a human, Ame already thought of all that. Unwilling to hurt the Pokemon, she reached her final conclusion:
If it comes to the worst, she would have to let it happen and be the ultimate sacrifice, the martyr-spider, so to speak, for the chance to bring Lin back to light.
It didn't work. The end.