I think it depends if the past moment deserves to have a real-time scene. If so, then, yes, flashback.
Some tips for flashbacks:
Start with a sentence making it clear that we are going into the past. Show we are in the past by using "had." Go one step farther in past tense. If you are writing present tense, then tell the flashback in past tense. If you are writing in past tense, then tell at least the first part of the flashback in past perfect.
As you pull us out of the flashback, make it clear we are in the present. Authors often start such a sentence with "now."
She plopped on the couch as her mind wandered to when she was five.
Her mother had just given her, blah blah
Now she sat up from the couch, shaking the memory from her mind.