All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If it is true that this woman had an emotional relationship with your husband, then she has committed an evil deed. What is more evil is if she sought to spoil the relationship between you and your husband and cause the end of your marriage; this is the work of sorcerers and devils. Allah, The Almighty, Says (what means): {…And [yet] they learn from them that by which they cause separation between a man and his wife. But they do not harm anyone through it except by permission of Allah.} [Quran 2:102] It was narrated on the authority of Jaabir that the Messenger of Allah said: “Satan places his throne on the water, then he sends his troops to people. The closest devil in position to him is the one who causes the most mischief amongst people. One of them (i.e. from his troops) comes to him and says: ‘I continued to whisper to so-and-so until he committed such-and-such sin.’ Satan responds: ‘You have not done much;’ (this process continues) until one (devil) comes and says: ‘I continued to whisper to him until I made him separate from his wife.’ Thereupon, Satan brings him close to him and says: ‘Yes! You are the best.’” [Muslim]
The Sunnah also carried stern warnings for those who spoil the relationship between a husband and his wife; Abu Hurayrah, may Allaah be pleased with him, narrated that the Prophet said: “He who incites a woman against her husband (i.e. to spoil their marriage) is not one of us.” [Abu Daawood]
Shams Al-Haqq Abaadi said in ‘Awn Al-Ma‘bood: “The same applies to inciting a husband against his wife.” [End of Quote]
As for the fact that your husband has a positive image of her, then this is not strange. It is more likely for non-Mahram men and women to exchange sweet talk, act politely, and assume good manners in their interactions, even if this is not their regular behavior. In addition, Satan could be a cause for that by beautifying her for him or by any of such destructive weapons that he employs.
Ibn Rajab said in Fat-h Al-Baari: “Women could be the ropes of Satan (with which he chases men). Whenever a woman goes outdoors, Satan looks at her from afar (getting ready to use her to lure others into Fitnah (temptation) and beautify her in men’s eyes).” [End of Quote]
You should be wise and not react adversely to the current situation, or else you would be helping this woman achieve her goal. Rather, draw closer to your husband, beautify yourself to him, and live with him in kindness in order to protect your family.
As we mentioned earlier, if this woman sought to separate you from your husband or had a relationship with him, then she is sinful and shall be held accountable before Allah, The Almighty.
Allah Knows best.