Limiting one member to X number of posts per day?

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Currently have a bit of a situation on my forum. We have one member who suffers from a neurological disorder that means she has communications issues. This isn't a problem in itself, and we're doing our best to help her out, but unfortunately she's also posting with increasing frequency and posts which basically amount to spam (she replies to every thread, even if it's just to say that she doesn't have an opinion). Currently she's posting up to 60 times a day and increasing... she has almost 600 posts in under 2 weeks and it's starting to dominate the forum a little. A lot of members don't understand that she has problems / think she's rude and are either put off from posting or outright attack her for being too blunt.

Umm... not sure why I shared all of that (although advice would be appreciated if anyone has any, it's becoming an increasingly tricky situation), basically all I want to know is if there's a way to limit her to a certain number of posts in 24 hours? I've already taken the step of pre-moderating any threads she posts and only allowing them through if they're relevant (or, in many cases, if they even make sense) but I can't really do the same with posts... there are just too many and it'd be an unreasonable amount of work for the moderators.