>>76756034 (OP)
In this boat right now anon my gf is 5'5 112-113lbs. Very skinny, petite, has a nice ass naturally, but its untrained and could benefit from more weight and training.
Here's what I can say:
1. Have her on a good routine weightlifting routine, you have google to figure out what that is for women.
2. You need to be on top of her on protein, hydration, and calories.
Women are notoriously bad at guessing their macros and calories, make her protein shakes, help her track, etc.
I cant stress this enough.
3. Be patient, just like building a good physique for yourself, it will take her time, reassure her and keep her consistent
Furthermore, reassure her as she gains weight, if she's used to being super skinny and gets insecure about being bloated, or seeing gain around her stomach, compliment the thickness she's gaining elsewhere. Also more bluntly, do this while you fuck her as well.
4. Balance building muscle and fat for her, dont have her pig out and just gain fat, she needs both for your desired outcome.
5. Plant nicotine patches on her while she sleeps, so she won't leave you once she has a better physique and new found confidence
Godspeed