if something bad happened to her there would be tons of other signs anger for no reason change in sleeping patterns ,change in appetite,changes in her relationship with everyone around her,wanting to sleep with her parents or siblings again, not wanting to go somewhere that she loved before, acting out, overly sexually behavior for a five year or a sudden withdraw of physical affection, i know the signs very will as a abused child and a mother of a four year old with autism who couldn't tell us if something like that happened to her you can't just assume from one one situation that she was abused not that you don't need to ask her questions or watch for strange behavior but that's a big leap to make from what happened and if she was she always going to say nothing happened because she's ashamed or was threatened a visit to her doctor can check for usual signs of abuse even if it happened a long time ago
It may also be a good idea to be aware that sometimes when children behave like this they have been touched by others so check out who is alone with her.The neighbors have every right to be annoyed it is not acceptable ..explain this to her and also your other children ,how old are they ?
It's ok when kids are curious BUT IMO at 5 the fact that she brought the other child into a private room and closed the door says she knows enough. I would sit her down in a non confrontational way and simply ask her if anyone has done the same thing to her..This kind of behavior is learned. She has witnessed it or unfortunately it's been done to her. You just have to make her feel as comfortable as possibly when you are questioning her because she will shut down if she feels attacked or if she feels she will get in trouble..You definitely have to make her know that this kind of behavior is NOT acceptable and WILL NOT be tolerated. I'm not aware but she's probably in kindergarten or on her way to kindergarten. his is an issue you do NOT want to follow her to school. You will also need to sit face to face with the other child and parents if they will allow it to maker her aware of how serious the situation is. Honestly you cannot blame them for their emotions. You just have to make them understand that you are just as concerned as they are. I wish you all the luck in the world :) As a parent of a 5 yr old myself, my heart goes out to you!
i don't think you need to worry she's probably just curious did you ask her what she was doing and why? you need to answer the questions she has and let her know that it is okay to be curious and to ask questions to trusted adults but its not okay to touch people that way or for them to touch her that way and maybe an apology from your daughter and only supervised visits will help your neighbors concerns