How do i get my show hog to gain 20+ in 2 weeks?

My pig needs to be 45+ at weigh-in on May 21. She only weighs about 20 right now, and i have been trying to get her to gain weight fast. I have tried putting whole milk with her Champion Pig grower food, but she doesn't seem to like it. She isn't with any other pigs, but she is next to a pen of 3 larger pigs that will be shown at the same fair. My hog isn't nearly as large as them, how can i catch her up so she makes weight?