BIG question; do you LOVE her or just her ability to provide sex ? IF you DO, learn to cope and encourage her to participate to the best of her ability. IF she LOVES you, she will. If NOT, leave. I was in your circumstance 40 years ago .....EXACTLY. Realized I deeply loved her and every single thing about her with the exception of her asexual nature. She loved me as much and we compromise. NO REGRETS !!!
When I started dating and Mrs. Mirror Orchid reset as a result, we began to be intimate about 17 times a year (three weeks). This was not discussed. She just chose it.
My compromise is accepting this frequency of high quality intimacy. I'd rather it was two weeks, maybe more frequently than that even but considering we were at every three months and she quadrupled our coupling, I'm letting sleeping dogs lie.