الزَّانِي لَا يَنْكِحُ إِلَّا زَانِيَةً أَوْ مُشْرِكَةً وَالزَّانِيَةُ لَا يَنْكِحُهَا إِلَّا زَانٍ أَوْ مُشْرِكٌ ۚ وَحُرِّمَ ذَٰلِكَ عَلَى الْمُؤْمِنِينَ
The adulterer shall not marry save an adulteress or an idolatress, and the adulteress none shall marry save an adulterer or an idolater. All that is forbidden unto believers
Abu Dawood (2051) narrated from ‘Amr ibn Shu’ayb, from his father, from his grandfather, that Marthad ibn Abi Marthad al-Ghanawi used to smuggle prisoners from Makkah. There was in Makkah a prostitute called ‘Anaaq and she had been his friend. He said: I came to the Prophet (peace and blessings of Allaah be upon him) and said: O Messenger of Allaah, should I marry ‘Anaaq? He remained silent and did not answer me. Then the words “and the adulteress –fornicatress, none marries her except an adulterer — fornicater or a Mushrik” were revealed. He called me and recited them to me, and said: Do not marry her. Classed as saheeh by al-Albaani in Saheeh Abi Dawood.
It is forbidden to marry a Zani/Zaniyah. If you are fluent in Arabic, you can discern the grammatical difference between a Zani vs. One who has committed Zina. Zani/Zaniyah are individuals who are actively fornicating (Prostitutes, Individuals in the dating scene, etc). Allah is directly referencing Zani/Zaniyah - the ones currently being operative in the sin.
Therefore, unless the sister repents (search on how to make proper repentance/Tawbah) - she can only marry adulterers and/or polytheists. Indeed, the best solution to such a dilemma is repentance/Tawbah.
And Allah knows best.