At your age, I assume your partner is a similar age, I’d suggest Ammo and I’d suggest Instant Openness or Instant Shine and guess what you picked those too.
The bottle will last depending entirely on how much you use. If you use 1 squirt a day or 3 it’s going to be radically different. You need to find what works good for you and the person of interest and then decide from there. It’s safe to assume 2-3 squirts of each. so 60-90 days or so per 30ml bottle if one application a day.
Note: If she doesn’t want to have sex, pheromones aren’t going to change that. Go read What pheromones can do and what they cant Updated.
Note: You should respect any boundaries a partner places, if they don’t want to do something that’s their thing do not pressure them, respect their wishes.