Gaining

Don't be stupid about it. all you gotta do is..."forget". Don't mention it...dont talk about it...dont even think about it. Eventually. She'll stop looking for the signs. Always leave easy to eat foods out. Don't get them for her, see. just have them easily available, means you gotta eat em too..Infact, make her think if she doesn't beat you to the punch, she won't get any. When you make food. Make too much, then leftovers are abound, easy to heat up and you really don't even think about it.

Don't really increase the amount of food you buy. Just change it up little by little..

You'll do fine, don't make it obvious. lol

get some twinkies, bread them and deep fry them, it'll add an extra thousand calories per.

you could get some weight gainer and always keep it mixed with the chocolate milk you constantly have in the fridge. make sure she drinks a glass with every meal.

sounds a little strange, her wanting you to make her gain without her knowing. sounds awsome. does this also include encouraging her during or between meals?

here is an idea for a shake if she likes those, would be a good late night snake or desert. 1 pint Haagen-Dazs ice cream. 1 pint heavy cream. 1 jar Reese's peanut butter

Good luck, hope it helps