daughter crotch grabbing help?!

Question

Im so fed up with my daughter grabbing her crotch constantly or humps things. She is 3 yrs old and does it for the pleasure, sometimes its to go pee but more often than not its the pleasure. I understand its normal but I wont stand for it right now. When she gets a little older Ill explain how its normal and okay. 
Right now it’s embarrassing. Last night we had grand parents over and she grabbed her baby sister to play on the floor, but when her sisters hand accidentally came in contact with her vagina(over her clothes) she stopped playing and started rubbing her sisters hand on her crotch. Right in front of everyone too. I immediately grabbed her and took her in the other room and told her she needed to stop. She was being very deviant/sassy because she was overly tired and I dont think she cared about what I was saying. 
My baby just turned 1yr and I was planning to move her crib into her 3yr old sisters room but now Im worried. I know my 3yr old doesnt really understand everything but I also don’t want her grabbing or using her sister to explore herself. 
side notes…
I am a victim of SA from childhood so I have a LOT of anxiety around this kind of stuff. Im trying to be calm about and tell my daughter to quit grabbing and she usually does, but other times she wont stop. She is not abused, no allergies, potty trained etc. We just went to the Dr last month. Im also on anxiety meds.
Im a SAHM and literally with her almost 24/7, grandma occasionally babysits and thats it. Im extremely cautious with who is around her at all times from  my own history.

Answer

Idk that's really strange to me everyone on her talks about it's okay for kids to masturbate, but that's extremely odd to me. None of my 3 kids have ever touched themselves or anyone else like that. All they have done is try touch when I change diapers. I have NEVER in my life heard or seen kids touch themselves they way I do on this app...it's very alarming to me. I'll probably get ate up in the comments, but I feel like anyone under the age 6 shouldnt be doing that like that....call me what you want, but its weird. Also there have been millions of stories of kids being messed with & their parents said I'm home 24/7 or no one has been around them and it still happens. If this were my child she would have went to get checked the second she put someone else hand on her privates but I guess that's just me...idk what y'all got going on, on this app 🤯

Answer

Are you sure you arent projecting anxiety onto her ? Anxiety can cause kids to do that as well.

Answer

Kids will naturally explore themselves at that age. Don’t shame her for it, but the way I’ve handled this with my two babes is I will tell them “If you’re going to touch your private parts you need to go in your room by yourself for privacy”

Answer

From my experience the more attention you put into it the worse it is going to be. You need to let her discover her body on her own in a way she needs it. It is a process that you will see until she decides she needs more privacy for it. And that topic is going to come back in phases when they will have topic about body development at school later on.
So I am not concerned about the fact she does it to herself, I would however, talk with her about personal space and that you do not do it to others (in this case her sister). Explain to her why we do not do that when she is rested or make up a game with her that shows this kind of behaviour is not good. Also emphasise that when someone is violating her personal space she should be telling you straight away and teach her how to recognise it. 
So my suggestion is instead of worrying about what is happening naturally give her tools to avoid bad touch.