Sorry, hiddenhome - I think you're wrong. The pillow is filled with you smells and is attractive to her. It's a sign of a bond. The fact that you're a lousy, wiggling bedmate is just one of those things.
As I may have said before, the cozie household has very few rules for cats but those that there are, are enforced rigidly eg no going on kitchen surfaces, no scratching on unauthorized surfaces and - 'no biting in bed'.
They may be allowed to sleep with humans but I insist on good bed manners - even under extreme provocation. (Frankly, I'm a terrible bed wriggler/get up at 3 in the morning to read/ generally a pain in bed - so I'd probably think about biting me out of irritation if I was a cat who wanted to sleep.) But they're simply not allowed to if they want to retain bed privileges.
Next time she does it, even if it's 3 in the morning, just say - very firmly - 'BAD GIRL - NO BITING', and then put her out of the room. Pick her up if you can, or otherwise shove her out and shut the door on her. I know she's 15 but she'll still learn quickly.
A 20 minute exclusion would be enough for a Siamese to be truly penitent but I'll leave it to you to judge hers.
It doesn't mean she doesn't love you.