Is it permissible for a girl to seek divorce from her husband due to not feeling comfortable with him, and is it permissible for the questioner to marry her after her divorce? If that is not permissible, then when would divorce and marriage to her become permissible?

This woman must be avoided, and communication with her should be cut off, as she is a non-mahram and married. Your continued communication with her greatly increases the sin, especially given your precise description of her situation with her husband, which is among the secrets of marital life that should not be disclosed. It is authentically narrated in Sahih Muslim that among the worst people in rank on the Day of Resurrection is a man who has relations with his wife and then discloses her secret. If she is suffering harm, she has the right to seek divorce, but one must be careful not to cause separation between her and her husband, even through supplication, as this constitutes an aggression. If her husband divorces her, there is no harm for you in marrying her after her waiting period ends. A person should ask Allah to grant him a righteous wife, for Allah knows the hidden intentions of souls and the consequences of matters. "And perhaps you hate a thing and it is good for you; and perhaps you love a thing and it is bad for you. And Allah knows, while you know not."