Hair Rinse for Oily Hair

My oldest daughter, YuLan, has really thick, beautiful hair. It's also pretty oily-so oily that by the end of the day, she looks like she hasn't washed her hair in awhile. My sister and I concocted a simple hair rinse that seems to be really helping. Here's the recipe:

1/4 cup apple cider vinegar
1 cup water
10 drops tea tree essential oil
10 drops rosemary essential oil

Put ingredients in a plastic bottle. Shake well. Use after shampooing. Rinse out.