Skin So Soft by Avon is great for all kinds of bugs! I even use it on my grandchildren and rub it on my 2 cats.
Gnats do not like the odor of lemon or mint so perhaps your friend could spray herself and the area around where she sits with a mixture of fresh lemon juice and water or a mixture of mint listerine mouthwash and water. Neither are harmful to humans or plants or the environment.
If it is a problem while sitting around the lawn, try using citronella candles. You can get several metal buckets with citronella candle that lasts a long time at Family Dollar Store. Just place them around where the seating is and light up a few minutes before sitting down. Could hang a few from low tree branches if any are near the sitting location or set them on ledges, table or something that is head high, but not too close to the face. This will help control the majority in advance. You could spray the area with bug repellent before sitting down, but will probably have to repeat often. Remove any sweet smelling fragrances on your person prior to going outdoors.
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