Should I dump this poor friend?

We've been friends for three years now and more often than not we get in little slumps. They'll stop talking to me and act all secluded, just for attention. I'm always there for them and we're together alot, if not too much. They play little head games with me by hanging all over their other friends and saying crappy things. we're in slump three of the past five months of a sudden downhill in our friendship... its no longer fufulling, if i talk o them they wont listen, or theyll take it to harsh because they're hyper sensitive.. im lost