I know many law firms bill out for the services of the paralegal, legal secretary, etc. Other firms just build that cost into the lawyer's time. How much is your firm billing you out for if they invoice a client for your services? If they pay you $35 an hour, I would assume they are probably billing you out for much more than that. After all, they are also covering your insurance benefits, unemployment, social security match, etc.
You definitely would be losing money if you went independent and charged $35 an hour. Right off the bat, you get charged the additional 7.5% (that number might be wrong, it's off the top of my head memory) for matching for social security that the employer normally pays. As mentioned above, you would be responsible for doing your own invoicing, advertising, marketing, insurance, taxes, etc.
Don't shortchange yourself!
I would add a caveat to what was said above about geography. One of the reasons people can be so successful as virtual assistants is that their clients can come from anywhere in the world. Where you live doesn't necessarily matter unless you are actually looking for local clients.
Marie