Who is Rabia Al-Adawiyya, and was she a Sufi?

Rabia al-Adawiyya was a woman from the generation of the Tabi'in, who died in the year 180 AH. She was distinguished by her devotion and asceticism, and Sufism was not known at that time. The Imams of the Salaf, such as Sufyan al-Thawri and Ibn al-Jawzi, praised her. Some accused her of hulul (incarnationism), but Al-Dhahabi strongly denied this in Siyar A'lam al-Nubala', considering the accusation of hulul and ibaha (permissiveness) against her to be extremism and ignorance, and that whoever attributed such to her might be using her as a pretext for his own disbelief.