As long as she is still a legal owner of the house, then she has the right to access the home. If she is not currently living there, then it's possible that tenant/landlord rights might apply (even though you are a co-owner) - which would (in most cases) require that she give 24 hour notice before entering the premises. However your best bet would be to contact a real estate attorney just to be sure. You might want to consider buying out her share of the house if you aren't happy with the way things are going, as well.
Yes she should still be able to have access to her own house. Yes, you can change the locks but please make sure you give your mother a set of keys as it is her house too.
If you are concerned about your privacy or have something to hide from your mother then why not just buy her out. Give her the money for her half. Then you can change the locks again and NOT give her a set of keys.
As long as her name is on the title, she has full access to the house, no matter how much she owns unless otherwise specified in the title or some other document. If you restrict her access to the house, you are restricting access to her property and you may have to pay her a reasonable rent or restitution for it.
The correct legal answer: the house is your residence, without regard to your mom's share of ownership. Since she is part owner, she can enter the house but must give you advance notice --presuming she does not have your permission to enter. As you are the legal resident, you have "landlord / tenancy" rights protecting you. Do you REALLY want to take your mom to court? Pick your battles; get your "personal" stuff out of the house. You're trying to sell it anyway.