When her small child with an exploding bottle of ketchup came into contact with her designer outfit while on a beach holiday, Lisa Strandberg knew she had to get real. So the former Ford model turned booking agent and her sister Kaitie Sjostedt, an FIT alum who has worked for Herschel Supply Co. and LVMH Moet Hennessy Louis Vuitton, founded The Shore Line, a direct-to-consumer, women’s resortwear collection in…