First of all...
Even if you are right and she is wrong, it will not be useful to get upset or express anger toward her. You must remain calm as you make your points. Even if she makes claims that are wrong, getting upset (at least in front of her) will not help.
Regarding your question:
Generally NASA images are not copyrighted. You can pretty much do anything you want with NASA media (but not the logo).
http://www.nasa.gov/multimedia/imagegallery/"NASA still images; audio files; video; and computer files used in the rendition of 3-dimensional models, such as texture maps and polygon data in any format, generally are not copyrighted.
You may use NASA imagery, video, audio, and data files used for the rendition of 3-dimensional models
for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages. This general permission extends to personal Web pages."
http://www.nasa.gov/audience/formedia/features/MP_Photo_Guidelines.htmlhttp://www.nasaimages.org/"The NASA imagery offered on NASAIMAGES.ORG is generally not copyrighted. You may use this NASA imagery for educational or informational purposes, including photo collections, textbooks, public exhibits and Internet Web pages (personal or otherwise)."
http://www.nasaimages.org/Terms.htmlWikipedia:
I know many in education are distrustful of Wikipedia and given that anyone can edit it this is a reasonable position. At the same time... It's a wonderful source of information (and much of it is referenced). It has been a huge aid to me in researching topics as I've developed Universe Sandbox. Generally Wikipedia does a great job of identifying the copyright status of the images on their site.
In conclusion:
I wouldn't argue the point about Wikipeida, but would focus on pointing her to the terms of use on NASA's website. I did a search for "NASA images" clicked the 2nd link and then click on "Image Usage Guidelines".
Being a teacher is hard. It's much easier to just say get your images from site A and B only then to have to look up or check on the source for each student.
Be nice, don't get angry (in front of her) no matter what and let us know what happens.