If the two mistakes are intended to defraud the creditors, for example so as to suggest that your sister owns a different property worth substantially more money, then that could be a big deal.
But, the bankruptcy code
permits amendment of the petition at any time prior to plan confirmation -- so, it's not that big a deal, as long as the petition is actually amended.
Also, everything is relative, if we're talking about a huge percentage of the bankruptcy estate's equity being tied up in this one asset, then that would be a bigger deal, than if the equity is a small portion of the estate.
Regardless, a Chapter 11, unlike a Chapter 7
or 13, requires a lot of active attorney management. So, I would be surprised if the petition is not amended sooner, rather than later.
If you are concerned that the attorneys are potentially damaging your sister's future interests, and your sister is rejecting your attempts to help, then all I can say is that I admire your dedication -- but, sometimes, you must allow time for professionals to do their job. If this issue remains unresolved and it appears that the bankruptcy plan is close to confirmation, then I would yank your sister's hair and tell her to get a second opinion -- before it's too late.
Hope this helps.