Brother threateting at work place about a debt

[jay12]

State: IL

A friend of mine has a brother who added her as an add-on user on his credit card. My friend was a student, and used the card for her expenses. She did not make payments towards the card when she was a student. Later, her brother sent her a legal notice saying that she is responsible for the debt and that she clear it up. The balance was around 14000$. My friend is sure that she did not spend this big an amount on the card. It could have been interest and late-fees (?) that accrued. She does not have any records either. He even made her write a letter stating that she assumes full responsibility of repayment.

This happened around 3 years back, and my friend has been making regular payments ever since. Around a couple of years back, the brother sent a second legal notice asking her to either pay the entire amount in one go, or to take the account onto her name. She was not in a position to do either, as she did not have such a huge amount of money, and neither the credit history to take the card onto her name. What she did do instead was to almost double her payment every month since then.

Currently, the balance is down to around 9000. In the meantime, my friend changed jobs and moved to a new city. The brother somehow tracked her down (is this even legal?) and called her at her work place. He threatened her that the balance is still 14000 and that he would tell all her co-workers about this if she did not pay up! Can he do something like this? I do not ask if he can do this as a brother, but legally? Is it even legal for him to call her at her work place and threaten and harrass her? That too when she is keeping up her end of the agreement with the credit card company? She immediately called the credit card company and they confirmed that the balance is not actully 14000, as he insists, but a little over 9000$.

My questions are:

1. Is the brother legally right in threatening my friend at her work place?
2. What action can my friend take? Will she have to hire an attorney? (The dilemma is whether to pay high prices to an attorney or pay towards the credit card)
3. If she in fact decides to hire an attorney, what can be done? Can a letter be sent forbidding him to harrass her any further?
4. What retaliatory action can the brother now take?
5. What is to stop him from continuing to harrass her or contacting her co-workers?

We are totally at a loss, and my friend is very upset, understandably. Can someone help and give us some pointers?

Thanks for any guidance.