General

That's fine, but you'll probably need to tweak it later on down the line. After all, 1kg a week is 52 kg in a year. That's 208 kg in four years.

That depends on some things.
What is her starting weight? Is she already on the heavier side or your average size girl?
How aware is she of your preferences? Did you just say you would like her bigger or made her fully aware of your preferences?
How on board is she with it? Was she a bit reluctant when you asked or fully on board with it?
My advice is to just spoil her and let things happen for a start, if she is fully on board with gaining 1kg a week will result in aroud 50kg a year.

1 kg is defenitely a good start. Because she might like it, or she doesn't. If she likes it, you can make her gain more than 1 kg every week. But if she ends up not liking it, than it would be easier to either stop eating that much or lose the weight again