This is similar to Matthew, chapter 26:71, Luke, chapter 22:58, and John, chapter 18:25, with some minor changes. In Mark, it is the same servant-girl rather than a different one as in Matthew. In John, it was a group of people rather than one individual who addressed Peter. Mark said that this young servant girl or maid saw Peter again (καὶ ἡ παιδίσκη ἰδοῦσα αὐτὸν). She then began to say to the bystanders there (ἤρξατο πάλιν λέγειν τοῖς παρεστῶσιν) that this man was one of them with Jesus (Οὗτος ἐξ αὐτῶν ἐστιν). The message is not to hang around if someone is harassing you.
This is similar to Mark, chapter 14:69-70, Luke, chapter 22:58, and John, chapter 18:25, with some minor changes, as all 4 gospels have this 2nd denial of Peter. In Mark, it is the same servant-girl rather than a different one. In John, it was a group of people rather than one individual who addressed Peter. Matthew said that Peter went out to the porch area of the courtyard (ἐξελθόντα δὲ εἰς τὸν πυλῶνα). Another young servant girl or maid saw him (εἶδεν αὐτὸν ἄλλη). She then said to the bystanders there (καὶ λέγει τοῖς ἐκεῖ) that this man was with Jesus of Nazareth (Οὗτος ἦν μετὰ Ἰησοῦ τοῦ Ναζωραίου). Again, Peter denied it with an oath (καὶ πάλιν ἠρνήσατο μετὰ ὅρκου). He said that he did not know this man (ὅτι Οὐκ οἶδα τὸν ἄνθρωπον). Peter, the great defender of Jesus, again denied him in public with a solemn oath for a 2nd time, something he said that he would never do. Jesus had warned them about swearing oaths in chapter 5:33-37.