I think this might be helpful:
http://www.redearslider.com/respiratory_behavior.html
Open mouth breathing
This occurs occasionally, usually during basking. If it is frequent or accompanied by wheezing sounds or mucus, then it is a possible respiratory infection. Take basic measures and carefully observe. If conditions do not improve, then please contact a qualified veterinarian.
"If your RES exhibits any of these symptoms, then raising temperatures, quarantine and a water change would be the immediate actions to take. Ambient air temperature and water temperature should be raised 10 degrees F. Eliminate any drafts and cold air around the tank."
This site is like my bible! =]
I think the most you can do is crank up the temp. a bit and hope for the best. make sure to keep her environment heated (suitable for a turtle) and avoid any moisture that can promote the infection.
However, if her open mouth habit lasts for less than a minute it's most likely her yawning..
On a side note I had my turtle around the same time as you ..I got mine in January 2009. And when i saw your photos I'm like that turtle looks just like jojo :O