"I'm very happy. I spoke to Bobbi before the final and told her to go out fast, go for it and hold on.
"She didn't quite get her turn right but that will get better as she grows and gets stronger," Hardgrave-Booth said.
"The two girls who beat Bobbi were second and third respectively in the final of the junior world championships in Dubai last year. Bobbi didn't make that final but Monday night's performance reflects the gigantic strides she has made ... this is the highlight of her career," Hardgrave-Booth, who has coached her for seven years, added.
Gichard was rapt.
"I had absolutely no idea it was so close," she said.
"The plan was to go max all-out the whole way and hang on. Over the last few metres I was dying. When I hit the wall and turned I couldn't believe that I had the medal. Then I realised that I was so close to winning. It's great and I am so excited."
Gichard said the podium experience was special.
"I couldn't stop smiling, I looked around and Michael (Mincham, a fellow Kiwi swimmer) was pointing and holding a New Zealand flag which he gave to me. It is so cool."
The 14-year-old also drew praise from Australian world record holder Christian Sprenger, who was the television guest commentator.
"I can't stress enough how impressive that performance was for a 14-year-old against 18-year-olds. Not only that, but she was the youngest in the field and she took the race to them. It was mighty impressive," Sprenger said.
It was the first medal in the pool for the Kiwi swimmers this week.
Yesterday Gichard finished fifth in her 200m backstroke heat. Hardgrave-Booth said she needed to be four or five seconds faster to make the final.
"I don't feel too bad about it. The scheduling was a bit of a factor ... having the 200 so soon after the 100 didn't help Bobbi."
The 71-year-old, who has coached at Greendale for 24 years, pointed out the 200m is likely to become her favoured event. Gichard has her 50m backstroke event today, the 100m fly tomorrow and on Friday she will do the 100m backstroke leg of the medley relay.