Photos imported from an iPhone to a MacBook seem to only be thumbnails

I'm trying to compile my photo library on my MacBook Pro from external sources such as my wife's iPhone. When I use MacBook Photos to import the photos from her iPhone, they upload very quickly, but upon further examination they seem to only be thumbnails. A photo that was 1.2 MB on her iPhone is only 47KB after upload to the MacBook photo library. I'm thinking that it may be due to her iPhone iCloud photo setting. That since that is set to upload her photos to her iCloud account, the only photo file left on her iPhone is the thumbnail. I hate to be guessing though and am trying to find some confirmation that that is the issue. If that's it, will it be that if I turn off her iCloud Photo setting, her iCloud-stored photos will be downloaded back to her iPhone? So I could then upload them to my MacBook Pro? Don't suppose there's any way that my MacBook Pro could import her photos directly from her iCloud Photo Library?