I have whats app on my iphone and now my wife also wants it, so do I need to buy it again for my wife, even though my wife iphone uses my apple id but is synched on another laptop.
No. On her phone, App Store>Updates>Purchased...just download it directly on her phone.
not as long as she is signed into the same apple id. just go to the app store on her phone and go to the 'purchased' section, then 'not on this phone'. again, make sure she is signed into the same apple id that purchased the app.
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