Hmm...what comes to mind first is a TV show my DH and I were watching called Obsessed. It's about people with obsessive-compulsive things that control their lives and make them miserable, but they can't seem to stop. They had licensed therapists come and meet with these people over a period of weeks.
What seemed to be a theme was that these people had things/thoughts that would make them extremely anxious, say for one woman driving in her car. Or another person, going out in public. So, they adopted compulsive behaviors that provided them a short-term relief from the anxiety but long-term were not helpful to them at all. For example...checking the locks on the house over and over. Checking that the alarm clock is set, over and over, 10, 20, 30 times in the night. One man had a routine of kissing his dog 12 times before he went out the door.
What the therapists would have them do, is really get down into what the anxieties were, and what the worst case scenario looked like in their minds for this thing. What were they afraid of? And the therapist would gradually expose them to that fear repetitively to try to get them to gradually be desensitized to it. Also the therapist would have them sit there and basically expose them to that anxiety trigger, and have them "stay in the moment" and not try to avoid the anxiety, but to let it keep going until it eventually came down to a not-so-dire level. The therapist would say that the body can only sustain that high anxiety level for so long, and then it will have to come down.
So....again, this is only TV, but I wonder if it would maybe help you somewhat? To ponder what it is you are so afraid of with your dog, why it bothers you and what your worst fears are that will happen. Like, what might happen if you didn't watch her like a hawk? Sounds like you're afraid you would "lose it"...what would that look like to you? What are you afraid you might do if you lost it, or what you might think or...?
You could write these things down, itemize them, and then sit and see what it feels like to read them. Then, make a plan, for what you would do if any of these things happened again.
Say, ok, if she shows any of these symptoms, "I will immediately take her to the urgent care vet." Or, "I have such-and-such medicine I can give her to combat the allergies, so she will start feeling better very soon."
And say if worst came to worst and you did "lose it", who would you call? You could write down the number for the crisis line and post it near the phone. You could make a plan..."if I do get hysterical because my dog's allergies are flaring up, I will call a friend to come take my dog to the vet for me." Then just get away from the situation so you can calm down. Or put the dog in the bathroom and shut the door and just get away and go cry in your pillow if you needed to, until you felt better and could go and approach the situation with your plan.
You could even go so far as to let yourself think about what might happen if you didn't fix everything and make it it perfect.
I hope this rambling makes sense!! Just some thoughts...
~Hugs~