Is what the questioner feels—a bad impression of suitors—a blessing from Allah, or is it an Islamically forbidden bad impression, especially since it always turns out to be true for her?

It is forbidden for a Muslim to think ill of their Muslim brethren unless there are clear signs indicating it. Precaution is required in marriage, but it should not lead to obsessive doubts. A woman should consult trustworthy individuals about a suitor; if he is religious and has good character, she should seek Allah's guidance (istikharah). If what is happening is a matter of intuition (firasah), then it is a blessing that warrants gratitude. However, if it is an accusation without evidence, it is a bad assumption (su' adh-dhann) and a sin that may lead to being deprived of success. Allah Almighty says: "And whatever calamity strikes you, it is because of what your hands have earned, and He pardons much." One must be content with Allah's decree and destiny, turn to Him in supplication, and strive to find a husband with the help of righteous female friends or maharim. There is no harm for a woman in seeking a husband within Islamic guidelines.