Facebook undesirable friend

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Just a month ago My husband's classmate in high school saw each other on facebook. Since then they were exchanging messages and they talk on phone when my husband is away, I know these because when his home I read his messages if not deleted. One night my husband is sleeping and he got message on his cellphone I read it says "hello sweetheart" etc. so I hide his cellphone which he agree. After a week I gave it back his cellphone but again he just change the name of the girl and they are talking again so I hide again his cellphone. Now just the other day she is posting on my husband wall says "regards to you and your sons, I don't care if your wife don't want to be friend of me". She is pissing me off, so I blocked/remove her on my husband's friends. If that happens to you, what will you do? Will you do the same my friends?