Girlfriend says the gym is my other relationship. Is 6 days a week actually too much?

We've been together 2 years. I train 6 days a week, 90 minutes each, usually evening after work. That's my routine since before we met. She's not asking me to quit. She's saying by the time I'm back and showered and eaten, it's 10pm and I'm tired, and weekends I'm sore and want to sleep. She said last week "I get whatever energy is left over" and that stuck with me. Part of me thinks she's right. Part of me thinks the gym is the one thing that keeps my head straight. Guys who train seriously and are in a relationship, how do you balance this without resenting either side?