I studied 6 days a week; how long per day depended on what I had to do. Some days I could maybe get away with 2-3 hours outside of class. on Saturdays, when I did most of my work, I'd average more like 6-8 hours. I usually took Sundays off to spend with my husband, and I always made time to eat dinner with him (we lived together). The couple of weeks before a legal writing assignment was due and the 3 or so weeks before finals were exceptions to this, and I worked a lot more then.
No matter how much I or any other poster studied, law school is an individual experience. You may have to put in a lot more time than I did, or perhaps a lot less. I have a couple of suggestions. First, you need to ensure that you are very, very organized so that way you can make time for what's important to you. If you slack off during the week, and then don't do work on the weekends b/c your SO is visiting, that's a recipe for disaster. Second, the last poster said it: make sure expectations are clear. Your SO needs to understand your obligations and responsibilities, and not get insecure and needy if you don't talk to her on the phone for 4 hours when you have work to do. On the flip side, you can't use law school as a way to put her off - you need to be willing to make time to listen to her concerns and try to find a balance. Both of you must be open to communicating about this, and both must try to be as reasonable as possible.