Is it permissible for a girl who has had many suitors but was never engaged to go to soothsayers to determine if she is bewitched, or should she just wait for as long as Allaah wills?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

Going to soothsayers, fortunetellers and magicians is a grave evildoing that must not even be thought about, let alone practiced, for it explicitly contradicts the Islamic creed which calls people to believe in Allaah as the only Lord of the worlds, to worship Him Alone, sincerely, rely completely on Him, and to devote desire for reward, fear of punishment, awe, submission, seeking refuge and seeking help to Him Alone.

You should note that a person attains in this worldly life only what Allaah has decreed for him. Even if all people gather to change this decree, they can never do so. All fates were written in the Preserved Tablet and no further thing will be written in it until the Day of Resurrection.

Instead, you should keep yourself busy with supplicating to Allaah, imploring Him, performing religious obligations regularly, doing as many voluntary good deeds as you can and seeking forgiveness from Allaah continuously. Allaah the Almighty Says (what means): {And said, 'Ask forgiveness of your Lord. Indeed, He is ever a Perpetual Forgiver. He will send [rain from] the sky upon you in [continuing] showers. And give you increase in wealth and children and provide for you gardens and provide for you rivers.} [Quran 71: 10-12]

It appears you are not suffering from magic or possession, but only from thoughts that are whispered by Satan who wants to ruin your religion and your worldly affairs, so seek refuge with Allaah from him. 

Allaah Knows best.