The reason you want to be careful speaking with her is that you may be conveying messages you do not mean to when speaking to her, messages which will make her feel worse about any abuse that may have occurred. Usually that is a good idea.
This can still cause a sort of delayed harm, by the child being habituated to sex and sexuality which does harm similar to other forms of sexual grooming I mention above, by encouraging the perpetrator of the abuse to engage in worse actions later, or by the reaction of the child when they are older and realize the true nature of what they thought was harmless, or by the photos still being available and viewable after the child is old enough to be properly upset by someone viewing such photos sexually. That's when she just laid it on me. We were restless again and wandering through her house strumming the fuchsia strings on her mother's loom Ann's too-big-for-the-living-room hobby while Josie read me excerpts from a shitty fantasy novel, namely the "dirty" parts, the sections that said "breast," or "Can't I hold you the way I did last night? Do you have info about this? We'd rolled around before.
A Brazilian photographer has captured the faces of women before, during and after orgasms in a bid to 'break down the barriers of female. When I think about having that type of orgasm I think that it should feel researchers and the research done so far has been seriously tiny.
The majority of all child abuse crimes are committed by people these children know, love and trust. If for some reason her parents continually refuse to have her speak to a specialist then you may wish to look into more direct options, like contacting child services; since there is always a chance that one of the parents is abusing the child and actively resisting seeking help for the child. Then if the counselor tells you to go to authorities, do not hesitate to do so.
Depending on the child the fact that they were naked for this 'game' may not register as unusual or wrong, since nudity need not be associated with sexuality in a young child's mind. If so I would not push too hard on why or what happened, again as a non-expert you may risk use of leading questions which bias both her answers and how she views the situation; simply consider not forcing her to be alone with the individual until she sees a psychologist or doctor who can look into the odds of abuse and better help you to discuss the topic with her. In addition a child may try to convince themselves that they enjoy something that they actually find uncomfortable because they believe they should enjoy it, or they are disloyal or immature for not enjoying it, or because the only way to deal with something so upsetting is to convince yourself you like it as a coping mechanism. I don't want them to get in trouble, they are nice to me the rest of the time. Maybe it's like how people can't tickle themselves. It was moving -- sort of flexing and releasing. While it appears that this kind of ejaculation is a function of the paraurethral glands like the Skene's glands which comes through the urethra -- the same place we urinate -- and the fluid is a lot like urine, enough research has been done which finds this fluid to be very different from urine, even though it's possible some elements of urine are in the mix.