Ooooh.
That is neat.
I use a crummy cheapo vacuum sealed thermos from Ikea. It also rattles a bit, but waterbottle cages can bend...your friend should squeeze the cage around the bottle some (assuming she has metal cages).
I also have tried the Soho mug from Trek, but it's just a travel mug and doesn't keep coffee hot on a cold day.
I don't think I'd recommend it for the OP, either.
2007 Seven ID8 - Bontrager InForm
2003 Klein Palomino - Terry Firefly (?)
2010 Seven Cafe Racer - Bontrager InForm
2008 Cervelo P2C - Adamo Prologue Saddle