How do I import photos in OS X without using Photos.app? My girlfriend always used Picasa to import photos from the camera, but since upgrading to OS X 10.11 El Capitan that doesn't work anymore.

Using Photos.app, she is able to import the photos, but they're hidden away in a Photos Library file which Photoshop cannot open, meaning she cannot add photos as a new layer.

Any suggestions, please? In the open dialogue of Photoshop I've tried clicking 'Photos' hoping it'd show the entire photo library, but it doesn't bring up any photos.
You can use Image Capture in the /Applications folder. This allows you to select a normal folder and import photos to that location, which can be accessed in Finder or Photoshop as usual.

In addition, this application allows you to setup the preferred application to open when connecting your camera (or smartphone, ...). There you can select Image Capture itself as the default application.