I don't know how to handle this case, I have two junior brothers in my small town who lives opposite to my house, one help the other to create a trust wallet
The victim is just lazy. With Google, search, and a few minutes of reading, he can create a wallet. It is not too difficult.
100$ worth of Ethereum was deposited into the wallet
Don't deposit money to a wallet that you don't create it offline, by yourself. If you share or leak the wallet seeds to anywhere, anyone, you should abandon it. Create a new wallet and deposit money to a new one.
two days later the fund was moved out to am unknown address, after asking few questions from the wallet owner I found out that the other guy has access to the wallet too, I believe he did the dirty trick because he never warned the wallet owner to never share his recovery seed with anyone
Can't say. Naively and easily, you can say the friend is the scammer but no proof to support that. Because the victim can do other stupid things that leak private keys later. Anyway, $100 is a cheap learning fee fortunately.