Hello, card79!
Here's my female perspective on your dilemma.
I made the switch from 12# to 13# equipment in January of this year, just about a year after taking up the sport. Prior to the switch, I threw Storm and Columbia equipment ... didn't much matter as a beginner. When I saw what my husband could do with a bowling ball after the same amount of practice, I asked our coach why the difference. He explained to me that the cores in the heavier balls are different from the weenies I was throwing.
Before making the switch, I did a ton of research, looking at all the ball companies, and I discovered that Brunswick is the only one that doesn't use modified cores for the lighter weights. I ended up buying a Monster SmashR because the lanes we normally bowl are anywhere from medium to heavily oiled depending on who's running the machine that day. The SmashR has performed beautifully on any condition I've tried, including fried lanes after a weekend of open play/Cosmic crap and no lane care.
Oh, within two weeks of throwing the SmashR, my league average jumped 20+ pins. I recently purchased a Brunswick Inferno to try to step up again. But, had I known about the Monster Bruiser being released, soon, I might have chosen to stay with the Monster line.
Anyway, don't lie to your wife about the ball weight. That's just wrong! If she wants 13# that's what she should get. I started out with a 10# Ultra Hot that my coach said would be too light. He was right, and within a month I had bought the 12# Too Hot. Then I moved to a 12# Icon and improved a little bit. When I felt I was ready, I went for the 13#. Will I go higher? Probably not. I started this sport as a very out of shape 45-year-old. Now I'm in much better shape thanks to becoming hooked on this sport. But I really don't see a need to go heavier.
Right now I'm fifth on the high average for women list in our summer league. By the end of the summer, I'll be higher. And it has a lot less to do with the weight of the ball than with the accuracy I'm gaining. I've tried a 14#, and while it hits slightly harder, the accuracy just isn't there.
I've rambled enough for now. Hope at least a bit of this was helpful.
Deb