I presume that your friend had "keyhole" surgery, and that it all went well. I too had my gall bladder removed about 15 years ago. I was offered 4 weeks off work which I took, but could easily have gone back to work sooner.
For a day or so after surgery I had an aching pain in my right shoulder area. Apparently the surgeon expands your stomach/abdomen area with gas for easier access to the gall bladder, and when you deflate, a nerve which runs through the area and up towards your right shoulder gets squeezed causing discomfort but goes after a day or so.
I did find that the buckle on the standard Boeing 5 point seat harness could catch on the scar on my navel, which hurt, and I also found that some twisting manoeuvres would hurt one of the two smaller incision scars on my side.
You obviously already know about what not to eat, and when! I avoid fatty or creamy things FWIW.