An older gentleman would most likely be the best way to start her in this lifestyle. An older man would know exactly how to treat her and would most likely make sure that she had an orgasm long before his own, treat her as a woman, not as a slab of meat to get off on which is a terrible way to introduce a young woman to an amazing way of life. Experiences like what she's had so far could jade her from ever wanting to take these experiences any further.
Someone in their late thirties or up would most likely be best because most older guys are not just more experienced but they are also more laid back, relaxed and will work on getting her to relax and enjoy the act of having terrific sex, not just "fucking" or a BJ and run. Most younger guys just want to get on, blow their load and take off not caring if the woman enjoyed it or not. Now I'm not saying that's the case with all younger men but it most definitely is the case with most, just as I used to be when I was in my teens and twenties etc. Don't allow that type of thing to happen to her again or you could find that she'll just shut herself down to any more of your requests to have her play with others. In a short time she could be loving this lifestyle and having the time of her life. Just a thought for you. 🙂