[PiZdETS]

Here's my guess at what she's worried about; she loves you and your riding scares her, especially sportbikes as everyone knows they're about speed and performance- risky endeavors.
She's coming to terms with her own mortality and just like any good wife, doesn't want to live the rest of her life without you. She wants you to switch to something like a cruiser so you'll go slower and take fewer risks, probably wants you to give up riding all together but knows you love riding so that's too much to ask.

If you're taking her argument at face value it's easily disputable, look up some of the current professional racers who are in their 30's, not many past about 35 but still a few that are up there, still competitive, still not dead. Without meeting you though I can't really say. Some 80 year olds are just as quick physically and mentally as I am, most 20 year olds arent so it really has to do with how badly your mind is atrophying with age.