Is a rental lease valid if the leasing agent or landlord did not sign the lease in WA state

Why would your friend want to move in with a "boyfriend" that tells lies about her? Perhaps this is a good thing. If she does not have a signed agreement from the management company, then she does not have an enforceable written contract but may have an oral contract. Trying to determine what an oral contract may be difficult and not worth the effort.

As for telling lies about her, she may have a civil claim against her for slander and defamation. She would have to prove that she has been damaged because of the lies. The primary defense against such a claim for him is truth, so if the things he said were unflattering but true, her claim would fail.

To be valid, there must be an agreement (whether oral or written) with someone with authority to enter into the contract (usually with an ownership interest). So the question is, who came to an actual agreement with the boyfriend and friend, the management company or the leasing agent or both? And did that agreeing party have the authority to enter into the contract? It appears from your facts that there was no written agreement signed by both sides - oral agreements are harder to prove. Good luck.