Yeah huge mistake to buy one for yourself, you will never hear the end of it until you give in.

As far as why, because from a young age they were taught not to think for themselves... So the message of you have to have an Iphone and Ipad if you want to be anybody, is not questioned at all.

i personally hate iphones. I would like one so i could play angry birds, but other than that... its a badass device that just makes people needlessly use their time to check their email when they could be enjoying the overpriced latte they just bought with a friend

I thought you were ditching her? Christ... tell her to buy her own damn iPhone and change your locks... with her on the other side. 

very simple, tell her you will get her an iphone if she has a 3some.  

iphone and apple products have come to represent wealth and power to those without wealth or power.
but this actually has more to do with face. (hear me out)
females in china have been brought up with the idea that they are unimpotant. that their job is to serve country, parents , husband, and son,
the life of a girl can be broken down into these stages (i cant count at the minute)
1. learning how to attract a rich bf, learning how to be a good gf and wife
2. attracting a bf
3. being a good gf
4. being a good wife

lets key in on 3 . one of the female's task as gf is to give the bf head when ever she can. i mean give him face , give him face whenever she can. she does this in part by trying to behave like a child. this gives the man face by making his "stature" seem bigger by comparision. imagine if you will a bar graph. imagine the man's " stature" at 3 inches or so. if the female lowers her stature lets say to a -4 the man's "stature" by comparsion appears to be a 7 by comparision. and that's quite appreciable. 
the female lowers herself as stated before by acting like a little girl. there are many ways to do this. one way is by throwing public tantrums. think back on the times you have seen this in the street. the female will be very theatrically twirling about and dramatic. while the male is quite poised. remember you lose face byy behaving emotinal. so she is throwing a tantrum like a 10 year as a way to give him head in public , face i mean face. give him face in public by losing face. you will always see gawkers , they are observing and calculating how much head he is receiving. i mean face. how much face he is receiving. 
but the most important way a female gives her bf face is by pouting. we have all seen the woman walking around town or in a mall dressed in expensive clothes on her expensive iphone. she is always stunningly beautiful but there is one thing off. she has a permanent pouting facial expression . these are the best of the best, that is how they land the rich bf to buy them these expensive things. mom was right when she said if you keep making that face it will get stuck that way. mothers have used this to create these first class pouters. now with cosmetic surgery the pouting expression has risen to be the top seller. here is why pouting is the number one way to give a man face. poutng causes no lose of face for the female. so her unlost gets adding to the face of the bf. this is a way to give the bf maximun head in public without getting any on her face. 
getting back to the iphone, this offers a duel way for your gf to give you face. she will walk around with you pouting and throwing tantrums until you buy her an iphone. but you will not stop getting face after that. everytime she walks with you she must have the iphone out playing with it. this allows you to gain face because your gf has the symbol of wealth and power to everyone without wealth or power. everytime you go out with her you will be getting head in public.