Measures to take for Teamviewer remote control on an iMac?

Hi all again -- my aunt got a message on her iPhone claiming it had been hacked and to contact a technical support number. Here's what happened (egads--I've told her to TRUST NO ONE, maybe she'll learn this time).

1. She called the number, they told her to connect iPhone to her computer (iMac). She did that.

2. They told her to install TeamViewer. She did that.

3. They told her to open TeamViewer, and tell them the ID and password that the program generates. She did that.

4. They then were able to remotely control the iMac:

A) They made the cursor move.

B) They flashed images on the screen which claimed to show data from her "hacked" iPhone.

5. They asked her for her iMac password. She was trying to find it...

6. They hung up.

Upon my advice, she unplugged her Internet and shut off the iMac. It's been taken to the Apple Store. They are going to check it out, but told her that TeamViewer is a "one time access thing" (I assume they mean that once it's uninstalled, the chance of a remote hijack is gone).

Question: what measures should be taken? I'm highly unfamiliar with how to check out a Mac in this instance. And does this mean that her IP address, other computers in her house are at risk?

From searching it appears that most threads relevant to TeamViewer on here are for PCs, and logfiles etc. are uploaded for checking. Thanks for any advice! -- and please move if this isn't the correct forum, thanks.

 

Thanks! I'm a PC guy and this is one of my go-to places, so that info helps. Thanks again!