You know, it might not be a bad idea to try some lubrication, if you really think penetration is the issue. Then again, if she has an obstruction, such as some sort of abnormal tissue development in that area she may have difficulty laying eggs, as well. You may want to get her examined, or try examining her yourself. If there are no obstructions, then lubricate? Hopefully someone who has been through this will chime in.
Are her poops and urates normal, and does she push them out without difficulty? That's a hard once to answer, I realize. Some of our chams really look like they strain a bit sometimes to get their poops out.