How to call out a lying friend.

I have a really close friend who feels a need to lie about basically everything. They are always little white lies but annoying none the less. For example she will tell me a story on Monday and forget she told me so will tell me again on Friday but all the details have changed!  I want to still be friends with her but want the lying to stop. I've alway just shrugged it off because I feel sad for her if she needs lie about her life to make her feel better about herself.  How do I call her out without  screwing up the friendship?