Girlfriend and I stopped having sex

Girlfriend of 4 years, off and on, doesn't want to have sex anymore. She moved in about 6 months ago, and in the last 3 months we have had sex maybe a total of 7 or 8 times. She just finished working 80 hours a week for 3 months straight at the beginning of October, but the last month hasn't gotten any better, just worse. Very tense, not getting along. We had a blow up fight last weekend, said a bunch of things to each other. Is the relationship over? Time to bail? Or should it try to be salvaged? She says I love you, I know we care about each other, but there is zero intimacy. I don't want to force it, but I don't know how much longer I can wait around. :( I can elaborate more if needed, but this is the quick short summary of it.