the primer should control it although you will get a bit of sweat through. Keep calm and blot it up with a cotton pad. Do this before you add foundation, but again if some comes through just blot it gently with the cotton and keep doing that, eventually it should stop, especially when the blot powder is on top, the blot powder can be used a few times without looking cakey, also you can pat a minute amount of primer on to problem areas, not too much though or the foundation will go patchy. If you can maybe get a seat near a window too. Tell your lecturer about the situation, but say it when your client or anyone else can't hear, as she may be embarrassed. Don't worry though, your not a magician babe!
good luck xxx