“Finder” photos recovery

When you turned on iCloud Photos, it was supposed to warn you explicitly that all those "Finder" photos would be deleted, but it's too late for that to help now.

They are called "Finder photos" (previously "iTunes photos") because they were forced onto the iPhone through a process originally invented for use loading music and photos onto iPods, which were much less capable devices. As such, they were wholly dependent on Macs (or later PCs) to download blocks of music and photos. When they required different music or different photos, a new block of that type would be downloaded by the program iTunes. Later, iTunes was dropped and the function was given to Finder. (Hence the name of the block of photos.) The primary library of music and the primary library of photos had to stay on the Mac so that a different block could be selected to download to the iPod (and later the iPhone).

That's all prologue to say that you'll need to find the Mac/PC from which the last block of photos was downloaded with iTunes or Finder to your aunt's phone, hoping that the photos she wants are still there.