Are you talking about apps you downloaded or ones already installed on the BB when you got it? I don't usually see activation codes in the box. If they are apps you downloaded then usually the codes get sent to you via email.
both of em. i cant use blackberry messenger(it is already installed when i got my bb) because my bb is not activated. same goes for the ones i downloaded like twitter and facebook.
Blackberry Messenger (BBM) and a number of other apps will require you to have a Blackberry Data Plan on your account in order to use them... it will cost your a little more, but it's the only way to really get everything out of your smartphone... call your cell phone provider and ask for a Blackberry rep... sometimes it can take a day or so to activate this, so don't expect to have it working right away, but talk to them first.
And I hope she purchased an UNLOCKED Blackberry... otherwise you are going to need to get the phone unlocked from the UK provider your Mom purchased it from, or another online unlock provider.