Adding someone on Facebook is generally accepted as a shorter way of saying "While on Facebook, I added someone to my friends list.
The statement is meant to express what site you were on (visiting) when you added the new friend to your friend's list.
Furthermore, when you "add someone on" a site, it's understood that you are adding the person "to your friend's list", which is why that part of the statement is not said explicitly.
Adding someone to Facebook implies you are creating a new account for her on the site.
english.stackexchange.com/users/3918/Shaun
The first sentence It was the first time a girl asked me to add her on Facebook is correct.
She asked you to add her as a friend on the Facebook website:
It was the first time a girl asked me to add her [as a friend] on [the] Facebook [website].
The second sentence
It was the first time a girl asked me to add her to Facebook is not absolutely wrong.
If you happened to be the sole administrator of the Facebook website and had the authority to add and remove people, then the sentence would be correct:
It was the first time a girl asked me to add her to [the] Facebook [website].
In reality, however, this is not the case.
You are both already on Facebook, you and the girl.
That's the preposition that Facebook usually takes (also off in some cases).
Thus, whether someone is sending a message, friending you/adding you as a friend, writing on your wall, etc.
, it's all on Facebook.
Examples:
I am being cyber-bullied on Facebook.
I practically live on Facebook.
I'm on Facebook every single day.
Can you believe she sent a message on Facebook?!
Can't you just get off Facebook for once?
I need to get that creep off my Facebook [wall]!
How many friends do you have on Facebook?
Add me on Facebook now!
english.stackexchange.com/users/2705/Jimi Oke
If you mean Facebook from facebook.com , you'll add someone on Facebook, since it is a website (or social network site).
english.stackexchange.com/users/222/miku
I prefer on , but think either one would work.
What we're really saying is, It was the first time a girl asked me to add her to my friends list on Facebook.
To and on are both part of the idea and we have two different approaches to making the friends list implicit.
english.stackexchange.com/users/3313/Jay
The idiomatic sentence would be neither of the options, but rather "It was the first time a girl asked me to friend her on Facebook".
I believe that the verbing of friend is still restricted to contexts where Facebook is in the forefront.
english.stackexchange.com/users/3542/Peter Taylor
Which one is correct and why:   It was the first time a girl asked me to add her  on  Facebook   Or   It was the first time a girl asked me to add her  to  Facebook
To add someone "to" Facebook or "on" Facebook
english.stackexchange.com
<word-choice><grammaticality><prepositions><social-media>
english.stackexchange.com/questions/9769
english.stackexchange.com/users/1446/Anderson Silva
The difference betweeen "to" and "on" Facebook is that "adding someone on Facebook" is generally accepted as a shorter way of saying that you added someone to your friends list on Facebook. "Adding someone to Facebook" implies that you are creating a new account for someone on the site. However, it is possible that either would work and be understood. Generally "adding someone on Facebook" is the accepted form. However, some believe that both "on" or "to" are acceptable. "to" can be considered as adding "to" the list of friends. Some suggest "to" is more appropriate if you are a Facebook administrator,but this is not the case as you are both already "on" Facebook. Some suggest using neither but instead using the verb "to friend" but this they suggest is restricted to Facebook references.
The difference betweeen "to" and "on" Facebook is that "adding someone on Facebook" is generally accepted as a shorter way of saying that you added someone to your friends list on Facebook. "Adding someone to Facebook" implies that you are creating a new account for someone on the site. However, it is possible that either would work and be understood. Adding someone on Facebook is generally accepted way to say "While  on  Facebook, I added someone to my friends list".  Adding someone  to  Facebook implies you are creating a new account for her on the site.
The first sentence - "It was the first time a girl asked me to add her on Facebook" -   is correct. Adding someone to Facebook is not wrong, but it implies that you are creating a new account for her on the site. It is possible that either sentence is correct, but it is likely that the first sentence is more accepted. The second sentence is not incorrect but implies that you would be creating a Facebook account for the girl in question.
You are both already on Facebook, you and the girl. It was the first time a girl asked me to add her [as a friend] on [the] Facebook [website].
You are both already on Facebook, you and the girl. It was the first time a girl asked me to add her [as a friend] on [the] Facebook [website].
Adding someone "on" Facebook is generally accepted. This is correct too if you are the administrator, but not if you are both already on Facebook.  Neither. Use the verb "to friend" although this is restricted to Facebook
Adding someone  on  Facebook is generally accepted way to say "While  on  Facebook, I added someone to my friends list.  Adding someone  to  Facebook implies you are creating a new account for her on the site.
The first sentence, using the preposition "on" is the correct answer. The second sentence is not incorrect but implies that you were creating an account for the girl in question. It is possible that either answer is correct.