We lease a medical office and have one spare room. Our docs want to lease this space to a non-medical tenant who works for one of the organizations who sponsors medical seminars and offers CME's for physicians (not just ours) who attend these seminars.

Since the person is not a medical provider and does not provide direct services for our clinic (no B.A. agreement?), is this acceptable within HIPAA rules. We would require a separate phone line, but I can't isolate her from our internet unless I require a separate internet account for her. I would also allow her access only when we are in the office.

What other issues do we need to be concerned with or should we not do it at all?

Isolate her from your internet? Of course you can. It's the signal that she would be sharing, and that's all.
She can use your signal from a router, without having access to any software you are using. She doesn't have to be on a network, if you are using a local one.

If you aren't sure how this works, hire a computer setup company or person to make sure.

I see no problem with her using a room in your offices under any rules of HIPAA, but you are the only ones who know what sorts of information is spoken and written throughout the common spaces, and how isolated from all that she would be.

So, she accesses the internet, if your wireless service allows access to your medical files and records, there is serous trouble.

Access after hours, also, you are to have all files locked and put away, when you leave the office, if you are leaving files on the desk at night, and information, not secured, you have other serious problems.

You will have to be sure, that they do not hear patient information, and people talking about patients illness and treatment.

You can give access to the Internet either wired or wireless. However, you have to make sure she cannot access any other resources on your network.

What other issues do we need to be concerned with or should we not do it at all?

I would suggest you just not do it, you will never be comfortable with this situation if confidentiality is an issue.