Mark twice quotes Aramaic speech, once as mentioned in the OP and the second time when he quotes the exact words spoken by Jesus during crucifixion :
Eloi, Eloi, lama sabachthani [Mark 15:4, KJV]
Matthew quotes 'Eli Eli ...' the Hebrew of the actual scripture from Psalm 22 which Jesus, in his passion, is speaking. But Mark gives us the actual dialect in which Jesus uttered the words.
It is evident from their content that the four gospel accounts are four different aspects of Jesus Christ and his ministry upon earth.
Mark begins his account, in Mark 1:2, by quoting from Malachi (first) and then from Isaiah (second) regarding the prophecies of John the Baptist, 'Elias which was for to come', Matthew 11:14, KJV.
Referencing Malachi first, the lesser prophet and, historically, the second to prophesy draws particular attention to the prophecy in Malachi 3:1 - the prophecy of the coming of a messenger of preparation and, then , another messenger :
and the Lord, whom ye seek, shall suddenly come to his temple, even the messenger of the covenant, [Malachi 3:2 KJV]
Thus Mark, in quoting the exact Aramaic speech of Jesus on these two occasions draws attention to the very speech of the Messenger of the Covenant.
It is his speech which will inaugurate the New Testament.
the words that I speak unto you - they are spirit and they are life [John 6:63 KJV]
The gospel, in its entirety, is the expression of the New Testament, the everlasting testament, which the Messenger of the Covenant, Christ, speaks.
Mark draws attention to, first, the way in which that Covenant is brought in when he draws attention to Jesus' words in crucifixion. He who said 'I and my Father are one', upon crucifixion, in his offering up, states 'My God, my God, why hast thou forsaken me ?'.
Through suffering, through death, through bloodshed, is the New Testament inaugurated.
And its consequence can be seen in Mark's drawing attention to the exact words of Jesus in the OP's passage - 'talitha cumi' : I say unto thee 'arise'.
The consequence of Jesus' being forsaken of God in suffering and death is the arising from the dead of many.
Marvel not at this: for the hour is coming, in the which all that are in the graves shall hear his (the Son of man's) voice, [John 5:28, KJV]
Shall hear his voice : the voice of the Messenger of the Covenant, shall hear his exact speech.
Thus Mark, by highlighting Jesus precise words in Aramaic, draws attention to the way in which the New Testament is brought in and draws attention to the consequences of that New Testament and, also, draws attention to Who brings it in and to the word by which it will be brought in.