When I text my friend who has my old iPhone I get the same text sent to my new iPhone as well. I reset my phone settings, but I think my info is still on there.  We already set up her information on the 4s.

How do I fix this problem without going thru the same process?

She also gets my photos uploaded to her phone with photo stream.  I had to turn off photostream on her phone so she doesn't get them.
Sounds like your friend's iPhone is still connected to your Apple ID. Tell her to go to Settings > iCloud > scroll to the bottom and tap 'Delete this account'

Better yet, have her restore from iTunes to get a completely fresh install — That's your best bet to remove all your information from the phone