If you're counting her calories together, here's a rule of thumb: if you add an extra 500 calories per day, she will gain roughly one pound a week on top of whatever else is happening. 1000 extra calories per day -> two pounds and so on. A lot of factors can affect this but it's a good estimate to start with.

You can get the calories from anywhere - fast food, home cooking, DIY weight gain shakes, etc. If she feels like she just can't eat as much as she needs to, put the calorie counting aside and just focus on stretching out her capacity. She doesn't need to stuff until bursting all the time, just extend a little bit past full as often as possible. Never any need to hurt herself or feel sick.

Starting from a balanced diet, every extra 500 calories per day you can eat/drink will roughly result in a gain of one pound per week. 1000 extra calories per day for two pounds per week, 2000 extra calories for four pounds and so on. This is subject to metabolism and other factors but it's a good working estimate.

The nutritional information on nearly every food you can buy is available online, or on the packaging. Look up your favourite foods and see how far each would get you if you stocked up on it. You'll probably find a few things you can enjoy a lot of.

If the funnel is held loosely in your lips and teeth rather than shoved down your throat, and the pourer is careful, you can taste it all going down. You just make the right kind of "mmm" sounds to signal your ongoing enjoyment.

A pound a week is perfectly feasible so take 19 weeks to eat healthy, exercise all you can and let others do the stuffing and gaining. You’ll be fine.

Once you started gaining weight, you would realise how mundane it is for a person to start gaining weight and how little most people care. As long as you weren't rubbing the "intentional" or "sexual" part in anyone's face, no one would think anything's out of the ordinary. Hell, it's a gradual process, try gaining 3-5 pounds and see who says anything.

If people want to be bitchy, they will, and it's not worth paying any attention. What might have a greater impact is when those close to you begin to worry about you.

A large factor in this is the assumption that weight gain is a failure or a loss of control, something you did not mean to happen or were actively trying to prevent. No need to say it's a turn-on, but if you say matter-of-factly that you're not concerned by it - or even like it - then people may be surprised but they'll at least respect your self-awareness and confidence. If they don't it says far more about them than you.

Liquid calories seems like the most straightforward solution as you can drink as much as you can manage as often as possible. Make a huge jug of something and keep it in the fridge. Here are some ideas: livestrong.com/article/438117-weight-gainer-shakes-with-about-4-000-calories/

Apparently this can happen completely by accident.

www.idsociety.org/FMT_Weight_Gain/

Non-dairy creamer can be just as good.

Why on earth wouldn't any of these work for anyone who can get them down?