I don't think what she is describing happened. I believe your 16 year old - who is blameless here - has no reason to lie. Also, this kind of thing doesn't usually happen in a compact car where he could be easily caught. I do wonder about the new boyfriend her mother has allowed to move in, and whether there is something going on there, with his kids or himself, or whatever.
Completely aside, you need to have a room for her. Whether that involves moving to another place, putting in a wall to divide a bedroom or living space in half (it can be easily removed to sell or reconfigure again, we did that and made two tiny rooms - worked great - got a contractor in for about a day and the room was divided). She doesn't have anywhere to "be" - and therefore, doesn't feel like a whole member of the family. Reason I say this, I have a friend (who is now 50) who was treated this way - she had to sleep on the couch for years because Grandma moved in and got her room, and everyone in the family had a room except her (some shared, but they had a permanent bed, not a couch) and she had a hard time recovering from that. In her adulthood, her mom asked what happened that made her feel so apart from the family, why she didn't fit in, and she said well I didn't have a place. I wasn't even given a bed. Everyone else in the house got to have a bed except her.
I really think this is important. As it is, she's visiting her dad, and visiting her mom's home, she doesn't really have a place to anchor. She doesn't even have a bed when she's at your home.
Weather or not the 9 year old was in appropriatly touched by your 12 year old she needs to go to a therapist that deals with children. If she is making it up there may be a reason why for example maybe she being inappropriatly touched at home etc.. I think it will help keep us posted.
No I always believe the child .unless its proved otherwise .it may be a good idea to speak to her Doctor
Right!! Something is amiss. I would never say I don't believe her but, at the same time the story doesn't add up. Do you think this is something a 9 yr old would just make up?
well in my opinion some thing is amiss...I think that there is something in this story and if it were me I would certainly be aware and keep my eyes open.I wouldn't put the blame on her, you probably will not get at the truth but definately make sure she is not left with them .as you say it is confusing and they may not tell the truth, all you can do is nip it in the bud and make sure if anything did happen it doesn't happen again ..good luck sounds like you have your hands full