Does the failure to overcome masturbation, despite repeated attempts at treatment, mean that God does not want me?

The sister who asked the question should forget the past and start a new chapter of obedience and righteousness, knowing that the sins of the past will not harm her as long as she has repented from them with sincere repentance. She must abandon her habit and have a firm resolve not to return to it, for Allah will assist and guide her, in fulfillment of His saying: "And those who strive for Us – We will surely guide them to Our ways." [Al-Ankabut: 69]. Sincere repentance erases all sins, and one who repents from a sin is like one who has no sin.

If she returns to sin, she must return to repentance and not despair of Allah’s mercy, and she should increase in acts of obedience and good deeds that erase sins, for good deeds erase bad deeds. If an opportunity for marriage arises for her, she should seize it, for it protects one's chastity. She should not surrender to intrusive thoughts and negative ideas, for they are from the plots of Satan. She should know that Allah is kind and merciful, so she should turn to Him and seek His grace and ask Him from His mercy which encompasses all things.