Is it permissible to send text messages containing advice and admonition to girls, with complete assurance of there being no temptation (fitna), absence of lust, and there being no female mahrams who have a prior right to such advice, and to limit discussions only to the matters sent, while avoiding personal talk?

It is permissible to send messages between genders for the purpose of enjoining good and forbidding evil, to the extent of need, while adhering to Sharia guidelines. It is preferable for women to call their female counterparts to Islam, as this is safer and further from temptation, for Iblis lies in wait for the son of Adam. Allah Almighty says: "Indeed, Satan is an enemy to you; so take him as an enemy. He only invites his party to be among the companions of the Blaze." And He, the Glorified, says: "And do not follow the footsteps of Satan. Indeed, he is to you a clear enemy."