Amanda Bynes Makes it Rain in Hotel Lobby

Amanda Bynes made it rain on the Sunset Strip Thursday night ... but not at a strip club -- in the middle of a hotel lobby.

Sources tell us Bynes attempted to snag a room at the London hotel as she meandered the streets on the Sunset Strip Thursday, but when she got there she was turned away. Amanda has stayed there before and caused big problems.

We're told Amanda became angry, grabbed a giant wad of cash, and tossed the bills into the air in the direction of the front desk.

As we previously reported ... Bynes plans to go to court today to get control of her life. She's trying to 86 her parents' conservatorship.