iPhoto not importing all pictures from camera roll (iPhone 6)

A friend of mine recently got a new MBP and was trying to import all of her photos through iPhoto, but iPhoto only recognized 200 something pictures out of the 2,000 she had on there. We've tried rebooting the computer/phone, getting the photos onto iCloud (which still only recognizes the 200 pictures), uploading her photos to Dropbox (which again, for some reason will only recognize the ones she has been able to import). I did do a backup to both iCloud and the computer, but we're reluctant to restore the phone in case the pictures don't get backed up, and she's afraid that she'll lose them.

If it's any help, the pictures that she was able to import were the more recent ones on her phone. Is it possible that the other photo/video files are corrupted? We updated the OS on her MBP and phone, so I'm really confused as to why she isn't able to import all of the photos on her camera roll...