My mom found a condom in my car!?

ok so mi ma was cleanin out mi car and she found a condom wrapper in my car! she askd was it mines and i said no... which is true it isnt mines. and she asked has n e one else been in mi car. i said no which is also tru other than mi friend key{she lives in germany and i only c her every summer}. and so im afraid to tell her it was key's condom and not mines.... but key hasnt had with anyone since she's been here... i dont want to tell on her but i dont want to lose mi car either!!! heeeeeeeeeeeelllllllllllp!!! idk what to do...