New mobile phone

If she was happy with the iPhone then maybe just step up to the iPhone SE 2 (2020) or SE 3 (2022) - They are the same size as the iPhone 6s, very similar design, but with more speed and features, as well as years more updates. It would be a very familiar device for her, and these SE Models tend to be pretty cheap especially if you make use of things like the current eBay discount codes that are going on right now.

If she wants to go down the Android route for a change, I would suggest Google Pixel. The 6A for example is a model that has a screen that isn't outrageously large, has a very well respected camera, and years of updates alongside decent performance without spending too much money again. If you want more, they have newer and better models in the range if you want to spend more.

The Honor is a good phone, And I have had a few of their flagships in the past and really liked them. But the Magic 4 Pro you mention is enormous. Especially if she is coming from an old style iPhone it's going to feed ridiculous to handle and if she doesn't have huge hands.

You said you want to get your wife a new phone, she's happy with her iPhone 6s so the logical sequence would be to get her the next iPhone upgrade such as the iPhone se 2020. Essentially the same phone but much upgraded components

Best not to rock the boat too much and keep things simple

If you're adamant about getting her an android instead, I'd recommend a Google Pixel 6A which can be had for £300 or less brand new or even cheaper used.

You haven’t mentioned a budget?

Take a look at Oppo Find X3 Neo. Very similar to P30 Pro in almost all aspects (albeit it has 90hz refresh rate).