It is makrooh to give a child the name Malak (“angel”)
Question

Allah has blessed us with a daughter and we called her Malak (“angel”). Is there anything makrooh in giving her this name? What is the Islamic ruling on that?.
Praise be to Allah.It is makrooh to use the name Malak or Malaak, and what you should do is change the name to one that is good and is not regarded as makrooh in sharee’ah. 
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked about giving the names Abraar, Malaak, Eemaan and Jibreel. 
He replied: The names Abraar, Malaak, Eemaan and Jibreel should not be used. End quote from Majmoo’ Fataawa al-Shaykh Ibn ‘Uthaymeen (3/67). 
Shaykh ‘Abd al-Rahmaan al-Barraak (may Allah preserve him) was asked about calling a girl Malaak and he said: It is better not to do it, for two reasons: 
1-What is meant by Malaak is malak (angel), and there is exaggeration in giving someone this name.
2-It is a name that is well known among the (Arab) Christians, who are the ones who say malaak for malak. There are so many good names with which there is no problem, that there is no need to use names that are dubious or problematic. End quote.
See also the answer to question no. 11228. 
Shaykh Bakr ibn ‘Abd-Allah Abu Zayd (may Allah preserve him) said: As for giving women the names of angels, it seems that this is haraam, because it is like the way of the mushrikeen who regarded the angels as daughters of Allah, exalted be Allah above what they say. Something similar may be said about calling girls Malaak, Malakah and Malak (all meaning angels). End quote from Mu’jam al-Manaahi al-Lafziyyah, p. 565. 
Based on this, you should hasten to change this name if you can. 
And Allah knows best.