Can I as a co-guardian and daughter be denied visitation to my mama who has dementia?

Yes, need to know whose house it is. If grandmoms then you have some say as to who lives there. To be honest, I would not wantva drug addict around my Moms belongings. If you share the guardianship, then sister cannot keep you from seeing Mom especially if Moms home.

Now if its sister's home, she can have anyone she wants to live with her and maybe able to keep u from entering her home. But asca guardian, don't think she can keep you from making sure Mom is OK and taking her out. I think you are required to keep check on Mom. This would be a question for the Court who appointed you guardian or the office you report to.

Sorry, I am confused. Can you please clarify? Is this your mom’s house or your sister’s house?

Your sister feels that she being supportive of her daughter. How is your niece doing in her recovery?