California yoga instructor and hiking enthusiast Jolly Bose had planned with two hiking friends to summit Mt. Givens in the Sierras on an 8-mile trip that should have taken just four hours to complete. But when the ambitious hiker on Oct. 17 became separated from her companions, the trip turned into an over-48-hour struggle to survive in freezing temperatures—this she did using an unshakable calm to adapt to the cold. Bose, 43, from Palo Alto, says the first mistake leading to getting lost was leaving her portable cell phone battery at home by mistake. She and her two friends Ken and Dmitry set out for the peak at around 1 p.m. and soon summited Mt. Givens, where they snapped photos together. Satisfied, Dimitri turned back, while Ken ambitiously broke from the plan and decided to tackle nearby Mt. Ian Campbell. Bose, despite not having downloaded the route map, opted to …