HappyTrekker

(I posted this in the Amtrak page, but maybe someone here knows the answer??)

Transferring CO miles to Amtrak then to United, does this work between accounts belonging to different people? (This works if all the accounts belong to one person)
e.g., could I transfer my CO miles to my Amtrak to my sister's United account? Or from my CO miles to my sister's Amtrak to her United account?

I tried to find out on Amtrak's website, but there wasn't anything.

Thanks for your help!