Law School Discussion

I know getting a letter of recommendation from an employer rather than a professor is discouraged, especially if you're applying right from undergrad (which I am), but will it really have a bad effect on your application? I go to a really large school where most of my classes range between 100-250 students, so it's hard to get to know the professors.  I have only ever had one small class, and I will be asking that professor for a recommendation.  For a second letter, I'd have to approach a professor who does not know me at all. I guess I could meet with her to talk a few times, give her writing samples, etc, but I feel like she wouldn't be able to write a strong, enthusiastic letter for me.  On the other hand, my employer knows me very well, she is a fantastic writer, and she really values my work.  So, is it better to take on okay letter from a professor or a great letter from an employer? I could get all three, but some schools only will take two, right? Thanks for your help!