I think you handled yourself just fine. You should be proud that you stood your ground and maybe you left your mom with some thought or two that will make her think sometime tin the future.
This board really is great! It provides the emotional support for the OP and for the everyone else lurking that feels alone and isn't comfortable posting. That can be seen by how much support ATA received on this thread and especially by a lot of newer posters who are going through similar situations themselves.