You know when body piercing exploded? When the Spice Girls became famous. That's when it crossed the niche, alternative lifestyle line, and it was mainly young girls demanding not only ear-piercings, but facial, navel and tongue piercings.
The market increased hugely. Also the rock and metal scene in the 80s and 90s was a huge part of the boom.
That's why you have a regulated industry, not just Claires and local jewellers, which has strived to improve practise and hygiene.
Another cultural trend brought on by the mainstream? Daith piercings - which may help migraine sufferers - publicised on possibly Loose Women as I recall? Which lead to a steady stream of very "straight" (as in not "alternative") customers, a large number of whom were muddle aged women. I'd like to see someone doing that with a gun due to its position. Cartilage piercings in general can take months to heal, and doing them with a gun can prolong healing time.
The point is, things progress and improve and the OP has asked for advice to make sure her daughter has the best experience and long term comfort which she has been given by a number of people, including myself and actual professional piercers. So it's up to her to weigh it up, and make that decision.
It may seem trivial to some, but we can never know for sure whether high standards in the industry has prevented a huge surge in infections and bad experiences in the last 20 - 30 years, but I'd hazard a guess that's very, very likely.
At least professional piercers give a shit about their predominantly female clients and don't just treat them as a useful cash cow using the least expensive and often sub-standard methods to squeeze money out of them. Personally I think that's a good thing.