My mom recently appointed my sister power of attorney over property that Im living in and to inherit upon her death. Can she sell house.

You may have to speak with an attorney about this.  The facts are unclear if the property is held by an irrevocable trust, then a power of attorney wouldn't be able to revise the trust.  You'll have to look at the powers of the trustee in the irrevocable trust.  Please contact an attorney.