No you have not been conned. You sign the Deed of Consent so that if your Mother is in arrears with the Mortgage they can repossess the house and evict both of you. The independent solicitor should be someone who is acting only for you and can give you advice as to your personal situation. Although it is sensible for you to use an independent solicitor you can just sign it and have it witnessed by your mother. It would still be legal but not in your best interests.