DXL - 9:57 am on Nov 8, 2012 (gmt 0)
The problem I see with using a stock photo is she'll be deliberately impersonating someone else.
The company that I purchase stock photos from is slightly vague about this.
If you have a legal disclaimer on your website that makes it clear that images used on the site can include stock photos, and aren't representative of your contributors/staff/clients, that seems to keep you in the clear.
The exception is when a photo is used in such a way that it puts the stock photo model in a negative light (random image used in an article about child abuse, or heavy drug abusers).
The short answer is that the stock company, photographer and model probably won't care if the photo is passed off as a portrait, given the author isn't writing anything inflammatory.