Have you ever heard of SAFETY, SAFETY, SAFETY. Sounds like your wife has long hair and did not follow the same safety precautions as someone with long sleeve clothing.
If she has short hair, why did she have it operating near her head?
Yes, I agree there should me a momentary switch for safety reasons.
If you use many power tools, they all have ventilation slots to cool the motor.
Was she even wearing safety glasses at the time.
You sound like the guy who sued a lawn mower manufacturer because they didn't put a warning sticker on the mower. He got his foot chopped off by the mower because he tried using the mower as a hedge trimmer. His position was "the manufacturer should have warned him from using this tool improperly" by placing a sticker on the mower. He won the case.
You get what you paid for. Don't blame them, blame the operator.