Is the wife entitled to seek divorce for harm when the husband’s family tries to convince him to marry another, and he agrees, and they hint to her that she should withdraw?

It is permissible for a husband to marry a second, third, and fourth wife, provided he is just between his wives, and he is not to be blamed for that. Do not rely on malicious innuendos from your husband's family. If you ascertain their intent to separate you, then pay no heed to them, for their endeavor is unlawful and a major sin. Strive to mend the relationship between you and your husband, and recognize his status and rights over you, for mending the marital relationship closes the doors to evil.