My dog has selective reactivity

Warning I have ADHD so I might ramble a bit but I will try to keep it short and sweet lol

I have a 4 year old mini Aussiedoodle that I got from the shelter at 4 months. She’s easy to train and was perfect up until she was spayed at 7 months old (vet recommended that I do that to avoid behavioral issues). After she was spayed she became VERY reactive towards people and dogs (never bit) and have bee working on correcting her behavior and we have made a lot of progress to the point she has made friends and can walk passed like 75% of dogs with no issue but once in a while there will be a fog that she will make her go absolutely insane. She hyper fixates on them her eyes get red she tries, she barks and jumps around. I try to walk away but she doesn’t budge. She’s on anxiety meds which has made her a little better but I would ideally like her to not react this way and I know she can do it but maybe my methods aren’t working. Like I said before she was easy to train and knows a lot of tricks and commands. She knows the basic commands, Recall, she does some agility courses and even knows numbers 1-6! So I know she can become the best dog she can be but with the right methods. I also forgot to mention she barks at strangers but once she’s alone with them she’s chill. For example we found a sitter for her and when we met the sitter she was barking at her and tried to get her to go away but then once I handed the leash to her and walked off she was fine and listened the the sitter but then once we picked her up she started barking at the sitter again eventhough they got along! It’s so confusing.

Any advice on how to handle this situation would be super helpful!

P.S. we have worked with trainers as well.