When it comes to her account with Koodo she can put it on seasonal hold for $15/month. This will hold the phone number and account. She will have to choose a new plan when she comes back though
You can choose to cancel the Koodo account but you will have to choose a new number (if the old one is no longer available) and pay off any remaining tab balance.
Agreed with Allan, David, BobTheElectrician and Goran!
If the tab balance is high, and you or your daughter are not ready to buy-out the phone subsidy balance, then the seasonal hold for $15 per month (plus tab) is the best option (meaning she won't be reachable on her Koodo number while it's on seasonal hold).
If there's no remaining tab balance, if the remaining tab balance is low, or you're just ready to buy it out, tt'd be far more cost-effective to port to Voip and either park the number there, or forward to a European number for the duration of the 5 months. Then take advantage of new activation promos when porting back to Koodo when she returns to Canada.
Do keep in mind that when she's back in Canada, she'll sign up for a new Koodo plan (with or without a new phone) with a new (temporary) number. I'm not sure whether the Koodo kiosk sales rep would be able to put in the port request. It's far easier to put in the port request to port back from voip to Koodo self-serve. Can take 2-5 days.