How can a woman overcome repeatedly falling back into sins after repenting, such as masturbation, watching pornography, and lesbianism, and regain the devoutness of her heart and her closeness to God?

Sins drag one another, and it is obligatory to beware of all of them, and to know that Allah is aware of His servant. Lesbianism is one of the grave sins, but truthfulness and sincerity in repentance help one abandon the sin. Relapsing into sin does not harm if it is followed by sincere repentance. Do not despair of Allah's mercy and increase your supplications and sincere repentance. Among the most important things that help in repentance are associating with the righteous and avoiding associating with the wicked, striving in supplication, increasing in supererogatory acts of worship, adhering to the remembrance of Allah, listening to admonitory lectures, reading books on spiritual edification, contemplating Allah's names and attributes, being wary of His wrath, and contemplating death and what comes after it.