to provide an answer to this old question, as it's still good info to have...
1) The best way at the time to delete the photos would have been to view the Last Imported photos and delete them from there. Not just deleting the duplicates, but deleting all of the photos (basically to reverse the import that was done).
2) What should have been done to import the photos from your wife's phone in to your library is to connect her phone to your computer, and import them from the phone itself, rather than the stream. This way, you are getting the original photos, not the compressed / lower quality versions from the photo stream.
iOS native photos app doesn't support dropbox sharing although you can open dropbox app in you device and add files manually. Make sure you have given dropbox permission to access photos.
Details:
Manual Upload
Step 1
Launch the Dropbox app on your iPad, and sign in to your Dropbox account if prompted.
Manual Upload
Step 2
Navigate to the folder on your Dropbox account to which you'd like to upload a file. If you'd like to create a new folder for your files, tap the plus sign at the top of the left column and then tap "Create Folder." Enter the name of the folder, and tap the "Create" button to create your new folder.
Step 3
Tap the plus sign at the top of the left column, and then tap the "Upload Here" button.
Step 4
Tap all of the files you'd like to upload to your Dropbox, as you can upload multiple files at once. A blue check appears in the upper right corner of the files you've selected.
Step 5
Tap the "Upload" button to upload the files to your Dropbox folder.
Automatic Upload with Camera Upload
Step 1
Launch Dropbox on your iPad, and log in to your Dropbox account if prompted.
Step 2
Tap the gear in the lower right corner of the left column to visit your Dropbox settings.
Step 3
Tap the "Camera Upload" tab, and then switch the button from "Off" to "On." Your photos and videos automatically upload to Dropbox from your iPad's storage.
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Best Answer
Use Google Photos. This being a fairly new app, it did not exist at the time this question was asked.
Google photos is a new (free!) service that allows you to upload all your photos to Google Drive, automatically. You can also share all your photos with anybody you want, using the new Share Your Library feature.
You can download the app from the App Store, or access them on your computer. There's also a desktop uploader in case you want to upload photos on your computer automatically.
The best part about this app is that it allows you to delete all the photos you uploaded from your phone, freeing up storage space on your phone. Your photos will still be available through the Google Photos app.