I have not had to do this, but I would not feel guilty, for a few reasons:
A) One can't responsibly rehome an aggressive dog, as it's a liability. Surrendering it to a shelter or rescue would be irresponsible, not to mention it would be taking the place of a non-aggressive dog who needs it. If keeping a aggressive dog isn't on the table, euth is the only responsible option.
B) If it's stressful for the owner, imagine what it's like for the dog -- it must be in a frequent state of anger and/or fear, which is no way to live.
C) Humane euth is not a cruel process. Humans have a lot of hangups around death, but dogs don't. There's no need to feel like putting a dog peacefully to sleep is a betrayal, especially not when one has exhausted all other options to improve its quality of life.
And that's all just from the perspective of helping the dog. The owner's mental state matters, too. Owning a dog will obviously have its ups and downs, and we all have to make sacrifices for our pets -- spending money on medical care when we didn't expect to, skipping out on trips or events when there's no one to watch the dog, stuff like that -- but no one should be expected to keep themselves in a constant state of stress and anxiety over a pet. It's not good for a person's health.
THAT SAID, in your specific case, it really sounds like your dog is resource guarding you, which can actually be trained away. You also say she's never broken the skin or even left marks, which means she's got great bite inhibition and is warning people, not trying to harm them. You also don't mention having tried any sort of medication to relax her, and you say that the techniques your trainer gave you are working, albeit slowly. I don't think I'd consider this dog a lost cause.
A) One can't responsibly rehome an aggressive dog, as it's a liability. Surrendering it to a shelter or rescue would be irresponsible, not to mention it would be taking the place of a non-aggressive dog who needs it. If keeping a aggressive dog isn't on the table, euth is the only responsible option.
B) If it's stressful for the owner, imagine what it's like for the dog -- it must be in a frequent state of anger and/or fear, which is no way to live.
C) Humane euth is not a cruel process. Humans have a lot of hangups around death, but dogs don't. There's no need to feel like putting a dog peacefully to sleep is a betrayal, especially not when one has exhausted all other options to improve its quality of life.
And that's all just from the perspective of helping the dog. The owner's mental state matters, too. Owning a dog will obviously have its ups and downs, and we all have to make sacrifices for our pets -- spending money on medical care when we didn't expect to, skipping out on trips or events when there's no one to watch the dog, stuff like that -- but no one should be expected to keep themselves in a constant state of stress and anxiety over a pet. It's not good for a person's health.
THAT SAID, in your specific case, it really sounds like your dog is resource guarding you, which can actually be trained away. You also say she's never broken the skin or even left marks, which means she's got great bite inhibition and is warning people, not trying to harm them. You also don't mention having tried any sort of medication to relax her, and you say that the techniques your trainer gave you are working, albeit slowly. I don't think I'd consider this dog a lost cause.