Basic Advice on Upgrading iphone 8 to 12

Apple no longer sells the iPhone 12. They currently sell the iPhone SE, 14, 15, and 16 models.

They also don't have the iPhone 12 in the Refurbished store: Refurbished iPhone Deals - Apple

There is a chance that some Verizon store might have an iPhone 12 in stock but I doubt it.

The following article has information about transferring her data. Transfer data from your previous iOS or iPadOS device to your new iPhone or iPad - Apple Support

I used the Quick Start method last time and it worked perfectly. Whatever method you use, have a backup. See: How to back up your iPhone, iPad, and iPod touch - Apple Support

ScreenLono wrote:

First, is it better to buy the phone from Apple or Verizon?

If you buy directly from Apple, it is easy to get a phone that is unlocked – one that will let you switch carriers later, should you want to do so. Basically, avoid carrier financing, and look for a statement on the order page (after you have selected everything) that says something like "Your iPhone will remain unlocked."

If you buy from Verizon, the phone might be locked to Verizon.

Second, best way to switch over to the new phone while keeping all of her photos ?

If she's using iCloud Photos now, setting up iCloud Photos on the new phone under the same Apple ID should do it, regardless of what stuff she transfers in other ways (restoring backups or using Quick Start).

If there are a lot of photos, it may take the new phone a while to synchronize itself against the master copies living in iCloud.

You can get more information here: iPhone - Apple