Or, you could try PolyGlow (sp?). It is a set that comes with a chemical cleaner (a mild acid wash) and a finish coat. The finish coat polymerizes, and stays glossy for about a year. We used it on 15 yr. old gelcoat to good effect. If your older gel coat is at all chalky, the Polyglow will help, but if it is not chalky, I think your best option is to ignore it, and quit staring at it, it's not really a defect.
I'd recommend against the paint option. I suspect it is just different batches of gel coat, and it will never match exactly, but try not to let it bother you, the boat will still work
just fine. And it will be obvious that you gave her gifts that constitute improvements.
A Visual distraction of brightly coloured cockpit cushions
well, as suggested above.