Is a rewritten will that has different signature valid?

My friend s sister left a will which states that all her assets should be given to my friend and her family in case she dies but it was rewritten on the same month her sister died. The beneficiary of all the assests on the rewritten will was another person but the signature was totally different. The prior will's signature was written in longhand and the present will was in all caps. My friend doesn' t know if the present will is valid. She is seeking for advice on what to do with the situation. My friend is a Filipino living in Japan while her deceased sister was an American citizen by naturalization and lived in New York.