My mother signed a quick deed to property in vt but has dementia can these be contested?

my sister in law has POA for now but i am the other brother going to probate court in conn for conservatory ship of my mother and is being brought to the attention of the courts about these. I did call the town clerk office and they are aware of these but have to file the papers when received,does anyone know of what legal action and how can i get these revoked as she is not in her right mind in doing so,But conn probate court wont do anything about these because it is in another state.Do i need to go to vt probate court about these or what?My sister in law and her husband( my so called brother ) they have basically used her social security check and had the property signed in conn over to them yrs ago now they are money hungry thieves.Instead of my mothers well being and using her property for sale for her care.