You have to improve your relationship with her and do training session at night or noon (on weekends) after 3rd session or 2nd, im not sure which u can click on the chairs in the back and go their, then click on the first chair to left and it will give you massage option.
Only after training session u get to give massage, read the dialogue carefully to know when to do it, after training 4 sessions, it becomes a choice, u either give her a massage or train, remember to actually read the dialogue dude
