Dicksorchard
Don't know about the landings, but the engine tone could be the autothrust system in operation.
On the A320 series, this seems to be quite active at times and if you are not used to it, can be surprising. It's quite normal.
If the aircraft was encountering turbulence, then the autothrust could have been dealing with that (maintaining a target speed) and the aircraft 'dropping' been a symptom of the turb.
I'm not in anyway being derogatory to your friend, sounds as if she was unlucky enough to take a rough flight.
Also, if she didn't like the state of the aircraft, she was probably a bit on edge anyway and noticing things she would not have worried about otherwise.
BTW, I am a frequent pax, but Beazelbub is a very experienced airline captain. He has given you a fair, but tough, response based on his research of the facts.
I have tried to take into account human factors in mine and soften the message, but essentially do agree with his conclusion.
PS: as an afterthought, during every year, I encounter a number of landings 'all over the runway', especially after the crew has landed on one wheel only!!!!
If I hadn't learned to fly, I might be concerned, but as a 'wing down' landing technique involves landing on the upwind wheel (into the strong cross wind that requires this technique), it doesn't worry me.
The 'all over the runway' feeling is the pilot handling applying liberal doses of rudder to maintain the runway centreline until the airspeed is low enough for the nosewheel to control the ground path.
In an ideal world, it would be lovely if the crew could brief the passengers about this (although some may be frightened), but in the rushed world of flying (lots of checklists and radio calls, as well as flying the aircraft in a busy environment), it usually can't done.