You should understand that Islam erases everything that came before it of sins and that repentance erases that which came before it.
Allah, may He be glorified and exalted, says (interpretation of the meaning):
“Say to those who have disbelieved, if they cease (from disbelief) their past will be forgiven”
Ibn Katheer (may Allah have mercy on him) said:
Allah, may He be exalted, says to His Prophet (blessings and peace of Allah be upon him): Tell those who have disbelieved that if they give up what they are following of disbelief, dissent and stubbornness, and they enter Islam, obey Allah and repent, He will forgive them what is in the past, i.e., their disbelief, sins and mistakes. End quote. Tafseer Ibn Katheer, 4/48
Al-Bukhaari (6921) and Muslim (120) narrated that Ibn Mas‘ood (may Allah be pleased with him) said: A man said: O Messenger of Allaah, will we be held accountable for what we did during the Jaahiliyyah? He said: “Whoever does good deeds in Islam will not be held accountable for what he did during the Jaahiliyyah, but whoever does evil in Islam will be held accountable for the former and the latter.”
An-Nawawi (may Allah have mercy on him) said: What is meant by doing good here is entering Islam both outwardly and inwardly and becoming a Muslim in the true sense. The one who does that will be forgiven for what he did previously when he was a disbeliever, according to the text of the Holy Qur’an and the saheeh hadeeth, “Islam erases that which came before it” (narrated by Muslim, 121), as well as according to the consensus of the Muslims. End quote.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
Just as Islam erases what came before it, repentance also erases what came before it. End quote.
Majmoo‘ al-Fataawa, 22/12
The one who becomes Muslim or repents from sin is only required to set straight the consequences of previous actions that he is able to set straight. With regard to these old pictures, the person in them will not be brought to account for them now, in sha Allah, so long as she has given up that haraam action. Rather all she has to do is remove whatever she is able to remove herself. As for contacting those who were her friends before she became Muslim and asking them to remove the pictures, that depends on whatever will best serve the purpose and what she thinks is most likely to be the case. If she knows that any of them would respond to that request and respect her privacy, then she may ask them to do that. As for those who she thinks will most likely not respect it or may become more stubborn or more interested in her pictures, she should not ask them for that.
If she thinks it most likely – according to what she knows about them – that they will not care about her pictures after she has left them, and they will not pay any attention to them, then it is better for her to keep quiet and let them forget about her.
And Allah knows best.