Service Dog

My best friend has a service dog to help with her disabling PTSD. She used to never be able to go into public places for more than 10 minutes without having a breakdown. I've seen the amazing transformation since she trained her service dog and although she still does have times where she struggles, her SD is always there to guide her to an exit if she starts having flashbacks or do deep pressure therapy to help control her breathing. 

My parents don't understand the difference between a SD and an emotional support animal. They think the dog would be for comfort and are like so pretty much you could just take Lucy (my current dog) everywhere with you. And i'm like NOOOOO!! she is not a trained service dog. she's a pet. 

Does anyone have any experiences with ACTUAL service dogs?? I need advice :/ HELP!