What is the appropriate supplication for God to choose for His servant all his provisions and affairs in life, such as pregnancy, marriage, sustenance, and anything else?

If a girl equates her choices and entrusts her affairs to Allah to choose for her, because He is aware of the consequences of matters, this is a good feeling. However, it does not preclude taking legitimate measures such as supplicating, searching for a righteous husband, and performing the Istikhara prayer when the supplication relates to a specific situation. One should frequently supplicate with general evidence for seeking provision and facilitating matters, while having certainty of response. For Allah answers supplications unless they are from a heedless, playful heart. Allah may hasten the supplication, or save it for the Hereafter, or avert evil by it.