I think you are referring to serious synthentic corks, not cheap ones in twist-off caps.
Assuming that they seal as well as real cork, I think they may be better, but until they have been used for some 50 years, the jury will still be out.
Rodney Strong makes rather full Cabernets, does he not? Never had one; just read about the winery. The lady in question may prefer a lighter wine, relatively speaking.
I don't know California wines as well as I do French ones, but Jordan may be the best bet, or a St. Julien from Bordeaux. Chateau Beaucaillou is excellent, or Chateau Beycheville. Chateau Margaux or Ch. Lascombes in Margaux go very well with lamb, in particular. I prefer the slightly fuller wines from St. Julien to Margaux, on the whole. If you're having a full-flavored beef dish or game, you may like the still fuller wines from Pauillac. Any major wine book will inform you about them, or Hugh Johnson's annual pocket guides. I think he still writes those.
If you need something less costly, try the better Chilean estates, like Vina Santa Carolina. They will knock your socks off, for the money. I have had some that nearly rivalled St. Julien wines, for far less money! In fact, I think they may surpass some Cru Bourgeois and other commune wines from St. Julien, which has an unusually high quality level for the entire commune.
In Californian wines, I have been very impressed by the Jordan estate. Also, by Stag's Leap. I met the owner some years back and asked if he had in mind to imitate Chateau Mouton-Rothschild. He admitted that this was so, and his wines have achieved very prestigious awards, even in France.
But I'd tell that lady to look hard at Cabernets from the best vineyards in Chile and at Columbia Crest and Ch. Ste. Michelle in Washington for best buys.
I can't keep up with who all is using synthetic corks now, but if these vintners or their close rivals are doing it, they must be okay, and be less subject to decline over the years than real cork. I share your dismay on finding a cork that crumbles on being drawn. If that happens, decant the wine and fish out any bits of cork before pouring.
Bon appetit!
T-Star