Messages showing as phone number rather than contacts

I recently bought my mother an iPhone 8 and it’s been fine, up until recently.

Over the weekend, when she goes into her messages, they’re showing as phone numbers, rather than contacts. When I click into messages from me for example, it’ll show as my phone number and have the option to add to contacts (despite being in there already).

I feel like this is a setting she’s inadvertently changed and I’ve tried a few solutions I’ve found online, such as signing in and out of iCloud, turning off and on short names and MMS in the settings, all to no avail.

Any help would be appreciated!