While the replies so far make much logical sense, this is something you need to remember:
WOMEN ARE NOT ALWAYS LOGICAL CREATURES!
I was in much the same position as you are. I tried and tried to explain it to my wife as well, but ultimately, she would not listen, and I ended up buying her a new ball (a black hammer).
I did, however, but my self one as well, and it was the exact same model she wanted to replace because she was told it was no good. (an lt-48)
When she continued to average about the same with her new ball, and I was still shooting 600 or better at times, with one like her old one, she got my meaning. She didn't like it much, and told me so, she also finally understood.
Times have changed a lot more than women have.