What is the ruling on marrying a Muslim woman residing in a European country who is seven years my senior and is not a virgin due to previous relationships, knowing that I love her very much and have sought Allah's guidance regarding marrying her three times, and each time my attachment to her increases?

Thank you for refraining from sins. Your love for this woman does not prevent marriage to her, even if she was not a virgin or committed adultery and repented, for marriage is the solution for those who love each other. Her mercy towards people and animals is a good quality, but it does not necessarily mean she is suitable for marriage. Your attachment to her after performing Istikhara does not necessarily mean that this is the result of the Istikhara; the crucial factor is whether there is divine facilitation or not. If marriage to her is facilitated, then proceed; otherwise, beware of temptation. She should have concealed what she fell into from sin.