Overview
SAF is a displacement grenade SMG, moving enemies around with her Skill.
SAF’s only purpose is moving enemies around vertically. This is not practical and having a Doll in your Echelon with actual utility or killing power would be far far better. If you want actual knockbacks that help prevent enemies from shooting at you, use something like LTLX7000, who knocks enemies away from you and does not have all the limitations on the Skill that SAF has.
Overall, SAF is a Doll that does basically nothing. As such, SAF is not recommended to even think about.