The DJ is a means by which the Riffs disseminate information to all the gangs in the city. The movie predates Twitter and Facebook. So to get information to all the gangs they use the radio waves.
It is not a main stream station. You are not going to hear her say "we got all that stacks of wax for you cool cats" or "Be the seventh call at to win a pair of tickets to see Fleetwood Mac".
The Warriors have no idea where the station is and just want to get home.

For the sake of plot and like others said, she probably got tips and reports.
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Oh come on she's reading the tweets and facebook updates as these gangs update their pages. Simple. Hahaha

This.
Pirate radio station, not a mainstream, public one. Besides, based on the "coded" language, most people wouldn't know what she was talking about if they heard it.

She's really just a narrator. But I'll play along.
One, the cops probably aren't listening in. Ever hear of pirate radio? She's probably not broadcasting on a major radio station and only broadcasting on a transmission that the gangs know about.
Two, gangs likely call in to hear about their exploits on the radio and bump up their own street cred. In this case, they're calling in to track the Warriors movements because the Riffs want them brought in or wasted and the Riffs are the biggest, toughest gang in the movie.
Three, the Warriors seem oblivious to the reports on the radio. And even if they had heard them, they don't have time to deal with it, they just want to get back home where they're safe.

You say the Warriors were not in a position to do that, but I am assuming that the radio station would not be heavily guarded and would very empty, wouldn't it?
Also if the radio host, was to blab all that in one night, the cops would have her under investigation, as she would be incriminating herself in gang activity, along with the gang who was feeding her information.
Why would the gang do that? Gangs do not give the media, progress reports on their activities. If a member of the media had gang ties, the gang would tell her to keep her mouth shut about what they do.

Plus Warriors weren't really in a position to do that. They were running for their lives.

She is associated with The Riffs - she is their semi-legitimate (hence all the code words etc) media organ.

She gets "anonymous" tips from gang members through pay phones.
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