Oh HELL on wheels.... Poor you!
Can you just put your foot down and say absolutely don't need/want any help.
Tell em 'Thanks for offering but NO'.... A firm no too, tell them you are prepared to fall out if need be. (It won't get to that, cos they aren't coming over..)
Your sis is totally taking the piss btw...
Moving is stressful enough, last thing you need is an army of spectators....