I am wondering how this turned out as I am going through the exact same thing with my 4 year old daughter right now! Thank you.
it could be misdiagnosed, though mono isn't all that uncommon. it's a bit more rare in such a young child, but it's happened before. Watch her temperature and make sure that's under control. many times for mono, they will prescribe a steroid treatment, so you can ask about that to the doctor if you want.