It sounds like she's trying to postpone or avoid getting tested for one reason or another. It's no question that you should both get tested if either of you have concerns about it, and especially if you intend to have sex with each other. Is she afraid that one of you might be tested positive for an STD and ruin the relationship that you have with each other? or maybe she's not ready to take it a step further, or doesn't want to have oral sex (or has had a bad experience with it) and is content with mutually masturbating with you? If she's avoiding the issue, it might be that she just isn't ready or is afraid of change, so I would figure out a way to ask her in such a manner that doesn't lead to her accusing you of being horny.
