I was married for 10 years to a man 25 years older than me... The reverse of your situation. He had absolutely no sex drive... The fact that we had 3 kids is something of a miracle lol! I naturally have a fairly high sex drive but I just learned to suppress it over time... What we had together was too good to let that become an issue between us. I don't know if that helps at all, sorry! Good luck :-)
My best ever sub was 50-60 years older than me, but I have no idea what to say that could help XD The only thing I can think of is orgasm control, maybe not chastity as such, just needing to get "permission" from her to do anything, you keep your high sex drive and everything, but it also makes her in some way involved with it? Plus it can be really hot, just a sugestion, obviously it's not for everyone.
That aside, have you talked to her? Communication is always important and you never know it might improve things :)