Possibly because they are intending to get together.
Answer
And because they are not nice people. A close friend, a real friend, would not talk about you behind your back ESPECIALLY with your ex. I would dump them both and find some nicer people to be friends with.
Although they are supposed to be your friend, sadly, doesn't guarantee that they are a true friend. They either lied because they truly wanted to do something to hurt you or had their best interests at heart excluding you or both, and friends certainly don't do things like that.
Because it is not scientific. There is no science behind. There is absolutely no scientific evidence in any of the things it is supposed to do.
In the poem "Somebody's Mother" by Mary Dow Brine, the two things that are contrasted are societal judgments about appearance and the realization that behind every appearance is a person with a story and emotions. It highlights the importance of empathy and understanding towards others.
Somebody who is nice to you face-to-face but says nasty hurtful things to others about you behind your back. Another term for people like this is "two-faced".
It is somebody to talk to that understands you. It is somebody that will always take your side. It is somebody to share things with. It is somebody to be physical and intimate with that cares about you.
Somebody who fixes things.
Somebody who finishes things is one who does things to completion.
Things that you have in common with somebody are things that you share - it can be something you are both interested in, something you both do as a hobby, or anything that connects you.
By being there. Your friend probably just needs somebody to listen to them and not try to judge or "fix" things or anything else. Just let them vent and get it out of their system.
No, people are not supposed to do things that they are not supposed to do.
Friends or best friends don't say terrible things about you behind your back. This person is not your friend and you need to confront them about this. There may be a chance that they did not say anything behind your back and the person that told you may be trying to split you and your friend up. Some girls can be very jealous over two other girlfriends that are good friends. Be fair, give your friend a chance to tell you the truth one way or the other. If she did say terrible things about you then you need to walk away from her as she is no friend of yours.
First things first: Your puppy does not know she is not supposed to do something. A puppy is like a toddler; if you don't tell a toddler that she can't reach under the sink where the chemicals are kept, she is going to think she is allowed under the sink. If you don't train your puppy to use the bathroom outside or to not chew up the furniture, she is going to think it is okay to do these things. Basically, you need to train her not to do what she is supposed to "know" not to do.