Go to http://www.rvwaterfilterstore.com/PressureRegulators.htm and order the 263A with gauge. At the same time order a 12" pigtail for the park faucets that are on the ground. Then get the Oxygenics (SP) shower head and she will be happy(camping world has the best price I found). Also get a regular RV water hose that is 5/8" ID. Wally World actually has a very nice hose with machined brass ends that is reasonable.
I set the regulator at 60 PSI and the large volume it flows thru the 5/8" hose is just fine.
I know in my case it wasn't really the pressure but with the low volume and low pressure combined, the stock shower head would barely spray across the shower. It goes without saying I was using one of the $15 inline pressure reducers.