My dd is the same age and is nursing very quickly now. Doesn't want to miss a thing. If I were you I would be (and I do this now) drinking a gallon of water per day & offer as much as possible. If she still won't take it & with drinking a gallon per day I was only getting 2oz I would prob stop. But I would save Luke 20 oz in case of illness.
I find if I nurse dd in a quiet place or while laying down she will nurse way longer.
Good luck & hugs mama!