The 44-year-old was also embarrassed she had suddenly attracted the media's attention, when it was her son who was making all the headlines.
While Hamish's father, former New Zealand captain Ken Rutherford, usually picks up some of the credit for Hamish's success, it was his mother Karen who took him to training and was there to encourage him when things were not going well.
When the Otago Daily Times caught up with Ms Broad, her son had moved his score into the 140s, but she was still feeling jittery.
''I'm really nervous because I know the pressure that is on him,'' she said.
''He has worked so hard, so to see him get to here and then to do this - God, it is a dream.
''I remember when he was 6 months old and from the moment he could sit up he had a little bat. We spent all day bowling to him. And Tom [Hamish's younger brother] was no different.
''It is overwhelming. I'm just so proud of him. He has just done so well and he is so confident and calm. I had a coffee with him this morning and he was just so relaxed.''
Meanwhile, Ken Rutherford watched every ball of the innings from his home in Johannesburg. Mr Rutherford works for South African betting agency Phumelela. He woke in the middle of the night to watch the end of England's innings then tuned in for New Zealand's reply. He repeated that on the second day.
''I'm a bit knackered, to be fair. The first half-hour was hectic,'' he told The New Zealand Herald.
''I saw him get off the mark, then I was glued, hoping he'd get to some semblance of respectability like 30 or 40,'' Mr Rutherford said.
''I kept my wife awake in bed I was so restless [watching the television]. My daughters also tuned in.
''I was most impressed with his mental conditioning. He appeared totally unruffled.
''I concur with what Stockley [Ian Smith] said in the commentary box about how he didn't change his expression or process out there.
''Both sides of his family are so proud.''
Just over 12 months ago, Hamish Rutherford's career was at a crossroads.
He had not played first-class cricket between November 2009 and February 2012. And with an average of just 11.90, his future did not look that rosy.
But he was recalled to the Otago team in March last year.
The 23-year-old left-hander grasped that opportunity with the following run of scores: 107, 118, 4, 39, 33, 67 and 239.
But yesterday was his greatest day. He scored a fabulous 171 to help New Zealand reach 402 for seven.
''A year ago I wasn't even playing for Otago,'' he said.
''So to debut like I have is very special, especially with a home crowd.''
- Adrian Seconi and Andrew Alderson.
