Is the wife's continued communication with a foreign man for whom she feels passionate love, while not neglecting her husband's rights and continuing her marital life for the sake of the children, considered a major sin?

What you are doing, speaking with a man who is a stranger to you (non-mahram), is forbidden and dangerous, and you must repent from it immediately. It is not permissible to speak with a stranger except for a legitimate need, and on condition that there is no fear of temptation (fitna). Islam has forbidden the means leading to fornication, as stated in the Hadith: "The son of Adam has his share of adultery decreed for him, and he will inevitably realize it. The adultery of the eyes is looking, the adultery of the ears is listening, the adultery of the tongue is speaking, the adultery of the hand is touching, the adultery of the feet is walking, and the heart desires and wishes, and the private parts confirm that or deny it." This matter is a trial, and patience in it and piety towards Allah will bring great reward.