Is it permissible for a girl to laugh and joke with her friends using emoji icons and hearts in comments on social media, and to converse freely amongst themselves? And if they do not respond to a request to stop doing so, is it permissible to continue following them?

There is no objection to girls using emojis in their private posts on social media, and there is no objection to them joking amongst themselves within permissible bounds. However, if these posts or conversations are not private to women and are viewed by men, then they must avoid anything that could incite fitna (strife/temptation). It is also necessary to avoid delving deeply and being excessively scrupulous in religious matters and asking too many questions about details, as this is blameworthy in Islamic law and may lead to waswas (obsessive whispering/doubts).