Iphone or Samsung s4 please need suggestions?!?

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Hello,ok so my cousin is 13 and she is a girl,and so she wants an iphone but her mum won't get it for her cause she thinks its expensive,and so she decided to want to get a samsung s4 but still her mum won't get it for her so she begged me to help her make her mum get one for her and please also does samsung s4 have instagram,keek and skype? Please help cause the main reason she wants an iphone is because she wants instagram and also she uses a blackberry 9900 which has none of those so please and also which iphone should she get and what is the difference between iphone and samsung s4 even though she will be 13 this september so please which do you think is best.and mostly she wants keek and instagram..thank you so much for your answers