Why my friend fell out with me over this wtf?

Discovering someone's actual name is no excuse for you to start using it when she has not asked you to do so.  Maybe she hates the name and that is the reason for shortening it. It is not wise to EVER use a different name, other than the one a person has told you IS his/her name.  Always wait to be invited to us either shortened name, pet names, etc.  Some names might be used only by close family.

Hello concerned one it probably was nothing you did on purpose that bothered her it probably was the fact that you put her private business as far as her full name out in space without her knowledge or permission especially if it would told to you as a friend thinking it would among friends only. Sometimes simple things are the most sensitive things to others just pray in time somehow she will speak with you again until then keep a calm heart and your peace. 

You didn't deserve that reaction, but my bet is, you pissed her off because you didnt ask her that but found out about it, could come off as creepy

She may have problems. If so, you may see this behaviour pop up over and over. Explain to her that you didn't mean wrong. At the same time, I don't know anyone who is called by their first and middle name, Maybe you should stick to first names. If she doesn't accept your apology, then don't contact her again.

Yeah, that was a real overreaction on her part. My guess is the other kids teased her about it as she was growing up. Ask her if this is the case, and assure her you didn't mean it in a nasty or juvenile way. Our childhood can carry over well into our adult years, so if this IS the case, please be understanding and comforting.

ok hun now I'm ngl, her name is awful! connie is cute but constance georgina is ******* hideous! so i can understand if she doesn't like her full name, or even just connie georgina, what i can't understand is how she reacted to you calling her it? i swear when this question popped up i had to read the details like 5 times and it wasn't til i read it for the 4th time that i realised it's real. i didn't even know what to say and still don't really! does she have anger problems or something? cos the way she reacted to this, it's definitely not normal! have i misread it and she's actually 14 while you're 12...i really hope your ages was a typo! if not she's not wired up right! you are 20 odd year old women ffs....she's pathetic! i wouldn't even bother talking to your mutual friend about her, she blocked you so just ignore her! that's what i would do, just let her be the big baby she clearly is, you deserve so much better! 

I'm embarrassed for you, I really am. I can't believe you two are in your 20s, this sounds like something a kid would sulk about. She's so immature! Are you sure she's the right friend for you? Really think about it, she can't think much about you to drop you over something as ridiculous as this can she? 

I think there is something seriously wrong with her to react like that to what was probably just a joke? And if she really hates her name that much, why does she display it for all and sundry to see? Very strange girl by the sound of things! You're probably better off being blocked, you're better off without her in your life if this is how she's gonna react to something as minor as this!

Yeah she did overreact. But at least now you know she’s emotional and short tempered so you can avoid her.

After reading this all I could think was wtf. If she doesn't like her name then it's understandable she wouldn't like you calling her that but **** me, you didn't know she didn't like it....why didn't she just tell you she doesn't like it instead of reacting so childishly! Seriously if she's really fallen out with you over this and thinks this is worth falling out over then she is not worth you spending anymore time on her it's laughable! The first thing she needs to do is get a sense of humour, but more than anything she needs to grow up! I'm 24...I feel insulted knowing there is a girl the same age as me who falls out with her 22 year old friend cos she doesn't like her name. I hope you're joking, or she's just playing but if not this is not even funny, it's pathetic