okay, my knowledge is limited, but let me try and explain what i know:
pulmonary hypertension means high blood pressure in the pulmonary arteries. basically there are little blood vessels that wrap around your airsacks in your lungs, and the airsacks then supply the blood in these vessels with O2, and that's how the rest of the body gets its oxygen -- b/c this blood then travels all over. in pulmonary hypertension, not as much blood can move through the vessels, so not as much O2 is getting to the body. the heart starts to work harder and harder to make sure that it can get the body the O2 it needs through the blood, and it basically just becomes a bad cycle. there are 2 types of PH: PRIMARY pulmonary hypertension, and SECONDARY pulmonary hypertension.
the doctors are talking about secondary pulmonary hypertension in your case, b/c it would be secondary to your daughter's CF -- in other words, caused by lung disease. here's the problem: once you get PH due to CF, it becomes its own monster, so to speak. curing the underlying disease won't cure the PH, so you would probably be referred to a cardiologist who would help your daughter manage the PH. the treatment would vary depending on how advanced the PH was. oxygen treatment is pretty common in PH, i think.
also, i'm sure this is WAY premature, but if -- in the future -- your daughter ever needs a lung transplant, that would also take care of the PH issue. lung transplant is considered a final stage treatment both for PH and CF, so it totally would not disqualify her or jeopardize the transplant in any way.