Would it be scriptural to refuse a widow benevolence because of very poor attendance at the worship services?
Are you talking about benevolence by individuals? Then it would be up to the individual to decide. Individuals are to do good to all people (Galatians 6:9-10).
Are you talking about benevolence by the church? Then it would depend on the reason why the woman is not attending regularly. If an otherwise healthy individual decides not to attend when they are able, then they are setting a poor example of what Christianity is truly about. Aiding someone who is not a committed Christian sends the wrong message to the world around us (I Corinthians 5:9-13).