Is the distress a girl feels towards a young man after performing Istikhara related to the Istikhara, or is it merely a psychological state? And should she have performed Istikhara for only one person? And is it religiously permissible for her family to force her to accept? And what is the religious ruling on this matter?

One should not rely on a dream after performing Istikhara (definition). Rather, the person who performed Istikhara should proceed with the matter for which they sought guidance. What becomes easy for them is hoped to contain goodness. It is permissible to perform Istikhara for more than one matter in a single prayer. A guardian does not have the right to force a girl to marry someone she does not desire. She should prioritize matters of religion, for a religious man is more likely to know her rights and make her happy. Finally, if marriage becomes easy, then that is good; otherwise, the forbidden emotional relationship must be severed.