Kent’s bowlers made the most of winning the toss as they restricted Glamorgan to 30-1 in the powerplay, with Young trapping Daisy Jeanes lbw for 15.
Parfitt struck two fours and a six, but when she drove rival captain Belt to mid-wicket in the 10th over, the batting fell apart.
With Kent bowling to their field, the boundaries dried up completely as no-one found the ropes after the two openers, and only Eve Jackson reached double figures as wickets fell regularly.
There was no run-rate pressure on the Kent reply with Streets and Gordon posting 33 in the power-play, although Nicole Reid then bowled her four overs for just eight.
The opening pair had virtually ensured the Kent win before Streets played on to Cobb, who had Gordon caught at mid-on in her next over.
But Rachel King (12 not out) and Maddie Blinkhorn-Jones (20 not out) made sure there were no further scares, and with rain driving in during the final minutes of the game, Blinkhorn-Jones belted Jackson over mid-on to seal an emphatic victory.