Hello Kengchi,
Welcome to the community!
Firstly, merely receiving the Welcome Abroad message does not necessarily mean she has incurred roaming charges. I was able to confirm that to be true here. The Fido Roam charge incurs when devices use Fido Services abroad.
In order to prevent unintended roaming charges, it is generally recommended to disable data and roaming data. However, she should note that disabling those settings does not prevent roaming for voice and messaging. In addition, some manufacturers might allow some data usage to occur despite those settings (see here). That's why it is also generally recommended to enable Airplane and/or Flight modes in order to prevent unintended roaming usage. She could then manually enable Wifi when required.
I understand she may have had Airplane mode enabled on her device. If functioning properly, that setting should have prevented her device from connecting to any cellular towers and she would not have received that text message. Is it possible she enabled Airplane mode after she arrived in Europe? If she did, her device could have connected to a cellular tower before she was able to enable the setting.
Now to answer your question... I don't think there is anyway to track your roaming usage in real-time (see here). As far as I am aware, Fido does not receive usage in real-time:
For post-paid roaming, when the user first switches their phone on, the visited network checks in real time whether the home network authenticates the customer and authorises its use abroad... ~ taken from here.
That would result in the Welcoming text message we receive when our phones connect to a foreign network.
...But the data records (CDRs) with the details on each SMS and data session are sent to the home operator with some delay (up to several days).. ~ also taken from link above.
If home networks don't receive usage information in real-time, it's not possible for them to provide customers with notification that a roaming session has begun without a delay.
The situation is different with pre-paid services where a real-time exchange is required to prevent the balance of the roaming customers' accounts from becoming overdrawn. That's likely the reason why pre-paid roaming often costs more than post-paid roaming.
For completeness sake, it should be noted that while using Wifi for regular internet access will not incur Fido Roam charges, there seems to be some misunderstanding regarding Wifi-calling. I'm not sure how people have gotten the impression that Wifi-calling does not use the networks. However, that is not true. While the calls and messages do not transmit via cellular towers, they still use the networks via the internet gateway (see image here). The cellular towers and Wifi are merely alternate means of accessing the networks. Calls and messages would not be able to complete or get sent/received without the networks. As such, using Wifi-calling is technically using Fido services. However, they have allowed certain usage to be free from additional charges. All the messages and calls you receive (from anywhere in the world) will be taken from your plan's voice minutes and messaging limits. As well, all Wifi-calling messages and calls you make to a Canadian phone number while abroad won't incur long-distance or roaming charges (see link above).
Hope this helps 😀
Cheers
Hello @kengchi , you are correct that you cannot monitor roaming charges in real time. The welcome message is triggered once you leave Fido's area of coverage, it doesn't necessarily mean there is a charge imminent. The most reliable prevention is to remove the Sim card as there are apps that will automatically connect to a network even though you're in airplane mode. I get updated weather when I put my phone in airplane mode overnight. You can turn off data roaming and use airplane mode and that might work. I don't risk the charges and keep my Sim card in my phone case until I want it again. Tracking real time would be handy, but fido has to wait for the networks that your device roamed with to send charges to them to determine what, if any charges there may be. Regards
