Judy's having a moment.
“Having a moment” is a very recent, modern phrase. It can mean taking a moment of peace and quiet to calm oneself down, from sadness or shock or anger, for example. It’s understood that if someone is “having a moment” or, more usually “taking a moment,” then it would be wrong and rude to interrupt their quiet moment.
“Having a moment” can imply that the person is known to have moments of being out-of-control, and so they are warning that she is ”having one of her moments” and you would be wise to stay away from her, so you won’t be hurt emotionally and/or physically. But,; “taking a moment” means the person is in full control of themselves, and you are being told not to bother them, because to interrupt their moment would be rude, or even harmful to them.
"be having a moment" would usually mean someone being angry or throwing a tantrum. Behaving in a manner that causes distraction or upset.
"swing" is slang for succeeding at something. For example to swing a deal - meaning to sucessfully conclude a deal .
"Having a moment" means "having a moment of working through one's own emotions." It could be a moment of reduced energy, to calm one's self down. It could be a moment of increased energy, such as anger or frustration. It's a moment of emotional intensity that is probably best handled alone.
In conversation, it's a coded signaling phrase from person or party B to person or party C, that person A is working through their emotions or problem should be left alone to let them do that.
If Judy is "having a moment," the rest of us should just leave her alone for a bit to let her work through some heightened emotions, likely due to a recent event that came as a surprise.
This is a relatively recent idiom. What you looked up in the dictionary is an older idiom using the same words.
Thank you so much for the clear explanation.