I suspect that your friend doesn't have a Hebe hedge, but one of the variegated Euonymus varieties - if its a low hedge it might be Euonymus Silver Queen, a taller one, maybe one of the Euonymus japonica varieties, but there are lots of others with variegated leaves. If your friend wants a definite ID of the hedge, then post a photograph. These particular shrubs have small flowers which are fragrant and which are particularly attractive to bluebottle flies. I'm afraid the only answer is to give the hedge a good clipping to get rid of the flowers.

I should maybe add that there are no varieties of Hebe with variegated leaves and fragrant cream flowers...

If they are blue bottle flies then there was something, somewhere in the hedge decomposing, probably a mouse. A blue bottle laid its eggs in the decomposing whatever and they have now hatched and become flies. They'll be gone in a week or so. She can obviously spray with fly spray but there isn't really any point.

Thank you.She had same problem last August then flies disappear. She will try spray

the flies disappear when the flowers fade. You can spray if you like, but all the time the flowers are out, every bluebottle for miles will come...