I do think your dog needs to see a vet, Dimitrije. Rapid heartbeat, the appearance of anxiety, hiding, and aggression toward other dogs can be signs of pain or illness. If she checks out physically, then perhaps the vet can give you some pointers on reducing her anxiety. But I think it's good that you'll be getting her to a vet for an exam.
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."