A weather app, I use breezy weather. And set up the widget.
Also definitely recommend Gboard, and if you enable faster voice typing and leave it with network permission overnight it'll download the language for speech to text offline, although it only works for some languages. But for any language it'll download autocorrect and word suggestion if you leave it overnight with that language enabled as one of your languages.
If she listens to music or podcasts get a nice foss alternative like Metro and antenna pod and transfer over her podcasts.
FindMyDevice if she often loses her phone, you can find it on fdroid.
An alarm clock app that feels more modern.
Locus for location sharing (fdroid).
A recorder app because it comes by default in most phones.
I strongly recommend magic Earth, it's a fantastic app.
Also, the dialer, SMS and contacts app have an old feel to it compared to the stock version. You might want to give her a third party app for those. (I happen to love the old feel so I'm not complaining)