Report him/her for afk and inting, below are the reasons:
#Afk
afk get's registered and counts up to a punishment. There is a well documented system around afkers.
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If you afk too often you have to wait for 20 minutes before the next 5 games before you can play. After the 20 minutes they put you in the regular queue and if you miss clicking the accept button you get to wait 20 minutes more.
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afk even more often and your account gets a 14 day ban or even a perma ban.
#inting
Inting is difficult tho.
This is mostly guesswork, but I can make a guess to how inters are punished. This does happen from time to time, just search the boards, they come here to complain(sometimes even false positives).
##Method 1: Stack based reports.
It would work like this, if a player get's reported for inting 2 or 3 times a player will be checked if they are actually feeding. If they catch them feeding they are getting punished. In this case you should report them since the inting is considered bannable you work towards a ban for that player. If she was not inting this should not punish her if she is innocent to it normally(considering scores like this normally don't occur).
Method 2: Checks placed in game.
By simply checking the locations of the deaths and the frequency you can pick out most of the inters. If riot does this you should report her, if she was indeed inting she will be punished.
That is why I think you should report her for inting and afk.