After defeating Lt. Surge in Vermilion City, I headed up into Saffron City. I took a little time to explore the city and chat with its inhabitants before taking on the gym. The teleporting pads were a pain (especially when finding my way out of the gym...), but I eventually made my way to Sabrina and defeated her. The Marshbadge is mine!
Spoiler:- Leader Sabrina was defeated!:
(Yeah, the attachment was an accident...)