The point is that for joint tenants, you each own half. If all the proceeds go to your mom, that is treated as if you sold your half and then gifted her the money afterwards. You still owe the gains tax because the gain is yours.
I also agree that if the home is held as joint tenants and you give your interest in the property to your mother, she will have to pay the gains tax on half the gain unless she owns both halves for 2 years.
You need to research how your deed is written.
