Does a girl sin if she rejects a suitor towards whom she felt unease and lack of acceptance after performing Istikhara and supplication, and is that considered a reason for her marriage being delayed?

It is permissible for a girl to refuse a suitor, especially if she does not find him acceptable, and there is no sin upon her for doing so. However, it is better for her to accept a man of religiosity and good character. Istikhara (seeking guidance from God) is recommended in marriage, and the prevalent view after performing it is to proceed with the matter and not abandon it unless God diverts it. Therefore, we advise the girl to perform Istikhara if a man of religiosity and good character proposes to her and she finds him acceptable. Then, she should not pay attention to any distress unless it is based on a clear reason, for God will choose what is best for her as long as her Istikhara was sincere. Refusing suitors might lead to spinsterhood if done without a valid reason, but if there is an acceptable reason, then there is no blame upon her. We advise her to supplicate frequently while maintaining good thoughts of God.