Let me tell you a cautionary tale. I had a similar experience happen where my fiancé at the time (we dated 7 years at that point) similarly did something that was so cold that all my love for her seemed to wash immediately from my heart. I made a series of terrible decisions— starting with staying with her— and got married - and later divorced and financially spanked.

Don’t stay if the love is gone. Not for the years you already put in, not for the convenience of being settled down. You will rob yourself of joy and you will be unfairly dragging her down with you. Sometimes it takes a major life event and witnessing how your partner acts under that kind of stress and pressure to realize that the relationship is unsustainable or that they may not be the person you thought they were.

Good luck and I truly wish you the best. This is an undoubtably difficult time, but it shall pass.