I don't think it's because you're posting messages too fast, it's probably because you're posting the same message over and over (which may be needed in a fast paced room).
I'm sure
we all
have seen members
who tend
to write
like this
when
posting in public
chat
and they never
get flagged
for spam
because every entry
is different
than the last
to the point
where there is a whole
page of messages
just like this
filling up the screen
all from one person.
That said, it seems like you need to vary what you say. Maybe have several messages ready for copy and paste, use one a minute? I would definitely ask MFC Support if they know how long of an interval you need to wait, and explain that you're helping out a model. If you have to post the message VERY frequently because there is that much chatter in the room, I imagine that she's rather successful, and they'd be more willing to help get an answer for you regarding that.
Good luck!