Most likely a water problem, particularly if the browning started at the outer parts of the plant and if its crispy brown rather than soggy brown. After years of gardening, I'm inclined to disbelieve people when they say they've watered sufficiently - you usually find they've walked round the garden with the spray gun on the hose in the evenings, and that'll never be enough to reach down to the roots of most shrubs if they've been in more than a year. Ask your friend precisely how she's been watering, and how often - this assumes the plant is in the ground and not a pot, and isn't a shrub over 5 years old.