Timing when sun goes behind a hill before sunset

hi! taking pics of a friend this weekend as a maternity gift. the location she’s chosen is gorgeous and new to me. the sun dips behind a hill 2 hours before official sunset. I generally love to start a shoot 60-90m before sunset but am wondering if I should treat that dip behind the hill as sunset? I’m worried light will be super harsh given it’s so much earlier than sunset. there’s some open shade but some angles / composition Id love that will be direct sun pre sun behind hill