Relief instantly floods Lapis when she hears Peridots' voice. Peridot is here, she'll understand, she'll help Lapis free these other lapis lazuli's imprisoned here. Or rather, that's what she thinks, right until her relief is replaced with horror when she finally regards Peridots' form.

The sound she makes is neither pretty nor relieved, and honestly, Lapis actively backs up away from Peridot as self preservation suddenly kicks into overdrive.

"Peridot?" Obviously this has to be Peridot, but it doesn't look anything like Peridot, and Peridot can't shape shift anyway, and none of this is making any sort of sense.