HELP! My renter in Paris is asking for 6 months deposit when I'm staying for 2 months

Hi, I'm a student from California and I'm going to be studying in Paris for the summer.

I got an accommodation, a shared flat but a private room in the 7th district. Right in front of Champ-du-Mars. I found the housing on the website badi.com. It was only 475 euros a month so I thought I found a perfect place. But, after I sent the rent for 2 months over with the deposit to the renter and signed off the contract, she asked me that I had to pay extra for health insurance and processing fee of 1700 euros. So I said I guess and sent the amount. Then again, she said that the notary cannot approve my stay unless I pay 4 extra months of deposit since I'm staying in Paris for less than 6 months. I asked her to share the flatmate's Whatapp because I wanted to get to know her better, then the flatmate added me and started talking about how I should trust her and send the money as soon as possible.

Is this only happening to me? I'm very skeptical about the whole process at this time.

I'd love to hear anyone's advice on this. Thank you