Is there a valid contract between these two parties?

Susan is the offeror of a Corvette and several times her friend Kannetha asks her to sell her Corvette to her. Susan is reluctant to sell Kannetha her Corvette because she thinks Kannetha will wreck it. Susan puts an ad on Craglist to sell her Corvette. Kannetha sees the ad and says, I accept. Susan tells her I don't want to sell you my Corvette, I believe you will wreck it.

Is there an valid contract between these two. and why?

When Susan put her car for sales on Cragslist, it is not an offer. It is called an "Invitation to Treat". Kannetha can make an offer and it is up to Susan to accept it. So, when Susan said, "I don't want to sell you my Corvette, I believe you will wreck it.", the deal is off.

Another example, you walked into a store and saw a Rolex watch with a price tag $120.00. You knew it is probably a mistake. You quickly went to the salesman and said I accept the offered. Do you think the store has to sell the Rolex for $120.00? The answer is no. Because it is not an offer from the store. It is an invitation to treat. You make an offer and the store has to accept it!

No the contract is not valid as the offeree rejected the proposal of the offerer.