Unlikely high usage - including when out of the country

[#1]

Mum's usage today - 2.43GB
She made no Skype calls at all, she was in a cinema for 4 hours, she did no web surfing she can speak of. A few emails. How is this possible? How can we find out remotely / team viewer if she has been hacked?
Also there was usage when she was out of the country, laptop closed and at home, last week Thursday- Monday 81.66KB 38.82MB 76.47KB 68.51KB and  69KB
Very puzzling - any ideas?

[#2]

Quote

Also there was usage when she was out of the country, laptop closed and at home, last week Thursday- Monday 81.66KB 38.82MB 76.47KB 68.51KB and  69KB

Those amounts are perfectly normal, they are small packets of keep-alive data and the amount of usage is tiny.

Quote

Mum's usage today - 2.43GB

1 or 2 decent length YouTube videos could easily use this amount. Any sites with videos that auto run etc would also be a likely candidate.