My daypack weighs 12 pounds a lot of times. Your pack is going to weigh at least 20-25 pounds, maybe more if you are carrying a gallon or more of water, more like 32 pounds. Not meaning to discourage you, just being realistic. 25 pounds is not bad to carry, anyway. I am only 5'2" also, have carried forty and fifty pounds when I was younger, although that is not recommended! :wlift: But if you can get it down to 25 WITH the water, it shouldn't be too hard to manage.
However, as advised before on the thread, I would strongly suggest you go somewhere above 7,000 feet in June or July! Hope you are doing Powell Plateau or other above-the-rim hike. If your hike is planned for June or July that means you don't have your permit yet. If you plan to go below the rim, the rangers are going to try to talk you out of it--they may even refuse to issue you the permit. It is just too hot down there.
There is a point of no return unremarked at the time in most lives. Graham Greene The Comedians
A clean house is a sign of a misspent life.