As a woman, I find women attractive, but I don't want to have sex with them. Just because you think someone is pretty, good looking, or drop dead gorgeous, doesn't mean that you have sexual chemistry. Most men lust after models, yet if they were to spend weeks with them, might realize that they like the picture, but have no sexual or chemical connection.
You like her as a person, you love her a person. Maybe really you are best friends. I don't see how couples therapy is going to help you have hot passionate monkey love if you've had 2 years together already. I'm not sure you can force that to happen, I am not even sure what makes passion what it is, when you can't really define it, and can't really explain it, how do you capture it with someone that you like and "make" it happen???? Passion happens naturally. I do believe some of it has to do with our chemicals in our body, our sense of smell, and how we react together. It's just so phuking fantastic when it happens that I can't imagine myself settling for a mediocre passionless life with someone.
I once dated the sweetest guy who adored me for over a year, but nothing he could do ever made my toes curl. So finally I had to walk away. But thankfully we broke up as friends, I didn't cheat of leave him for anyone else, we talked and we understood each other. Life is a journey, you are looking for something you don't have.
Passion and great sex is out there. I don't believe in selling yourself short or living a half life. But you need to decide what to do.