Annoying friend? help...?

Ok, I have this friend let's call her Jane and she's always saying how pretty she is but she isn't...at all. I'm a nice person so I'm like yes Jane, your beautiful! But heres the thing she says I'm ugly and fat all the time and not to toot my own horn but I'm a lot prettier than she is...and its really starting to piss me off...what should I tell her if this happens again? And don't say "don't talk to her again!" Because she is one of my closest friends...help!