While you said she is your bestfriend, she also happens to be a liar. Everyone lies and may also have reasons to lie, but not to the extent that it becomes your personality trait. And because you said that she is a liar, I guess she lies frequently to be called that especially by a bestfriend (you). No decent human would want to lie whenever they get the chance, rather they try to minimise it and avoid manipulating or hurting people in the process. Life is short, forgive her, but beware of her. Show her that you don't like liars subtly. If she doesn't change over time, start distancing yourself from her slowly. Don't cut her off immediately, she's still your bestfriend. I know it's gonna hurt, but leaving someone having good memories to reminisce is way much better than staying in a relationship full of doubt and uncertainties that may lead to resentment and broken hearts. Plus there are 7.8 billion people, +113 million living in Ethiopia, you're gonna find someone along your life journey, so cheer up☺️