John Allan wrote:
I agree, ask her as a courtesy.
But, you don't need a release to use these in your portfolio.
Since she's an agency girl and you guys are using the word test, she knows what test means. So there is a verbal agreement to each use for your respective collateral.
It'a not always that simple. Some states require that a model release be in writing. Oral or implied releases are not valid in some states.
Similarly, the rules vary by state as to whether you need a model release in order to hang an image on your studio walls or post it on your website.
Generally a release is needed if an image is being used to promote a product or service (this is sometimes called "Commercial use").
Non-photographers can usually post on facebook as there is no commercial component to the usage. A photographer who posts is using the image as an example of there work, this is a straightforward example of using the image to promote their photography business. The exact rules vary from state to state, and some states have specific rules when it comes to photography businesses.
The bottom line is that this is far more complicated than most people realize. The specific details of a situation are very important. Never take legal advice from the web. Always consult a local attorney for reliable legal advice.
There is also the issue that if the images get posted, the model may get in trouble with her agency. If the photographer and model are friends, he may not want her to get in trouble.