Crying in pack n play

My little girl is 7 months old and separation anxiety is kicking in hard. As soon as I set her in the pack n play she starts screaming. Carrying her is killing my back—and even with carrying harnesses and what not, it’s still not very supportive and limits how much I can do. Is it okay to let her scream and cry for a few minutes at a time? How can I encourage her/teach her that just because I’m leaving her side doesn’t mean I’m gone? Will doing so frequently help her get past this?

She is crawling and pulling to stand, so I can’t just leave her by herself when I need to do certain things like when I go downstairs to change out laundry