I'm sorry Sue has not been herself tonight and do understand why you are concerned for her, especially as this is so out of character.
The lethargy and fast breathing are a worry and, at her age, could be a sign if heart disease, lung disease or something else.
We would also consider stress from the loud noises (though this is unlikely if she has previously tolerated this well), an unseen toxin ingestion, internal bleeding, abdominal pain, a fever etc.
If she is not improving and her breathing remains rapid, it is important she is seen by a vet.
I'd want to listen to her heart and lungs and the vet may discuss some tests such as a chest x-ray.
However, if she seems to be acting more normally now and she is interacting with you and her breathing is settling, it should be okay for her to be seen tomorrow for a check up.
We want to ensure her gums remain pink (rather than very pale or white) and ideally her breathing should be less than 30 breaths a minute while at rest.