Do back handsprings in places you feel comfortable! on a floor line, up a panel mat, on the laser beam, and work your way up. Work drills for bhs on beams that aren't the full skill. Act like you are learning the skill for the first time. I'd say the same thing for switch leaps. Do it where you...
Along with floor line/laser beam, I'd always recommend working the skill upwards [like up onto a panel mat].
A big squishy mat. also might be called a portable pit/portapit.
I'm in Michigan, and meets will typically never cancel due to weather. Meets are an incredibly expensive, time consuming, and often thankless endeavor. If a gym were to cancel a meet they were hosting they'd be out the money for facility rentals, equipment rentals, catering for judge/coach...
Many needle kicks. One of the first exercises I have gymnasts/dancers do when teaching an illusion is needle kick, and then go in a circle using your hands to get around, just to work on keeping everything square. Also really work on getting your chest/shoulders/nose to your supporting leg in...
if she's doing well on the straps, then I would guess [without videos, hard to know] that it has to do with her wrist shift. Has she worked back extension rolls with a forster bar at all? IMO it really helps with the shift and timing.
Like the above commenter, I agree it's hard to help with giants without a video.
As for a back handspring on beam, work them on a floor line, work them up onto a higher surface, laser beam, put panels on either side of your gyms lowest beam so they're the same height and then lower the panel...