How to fix a scarf that was cut in the process of being made?

I’m knitting a scarf for my younger sister and i’ve gotten about one fourth of it done, but for some ridiculous reason, my sister decided to cut it when i wasn’t in the room. she cut the string of yarn mid-slip, and now it’s on the verge of coming loose. what should i do?? can it still be salvaged or should i give up and start over with some new yarn?

I am feeling very sorry for what happened to your project. Could you, please, make a picture of the damage as it would make it easier for us to help you?