Peridot can't exactly help Gon with that tail, but she can and will get that sword out of the picture... whether Sans lets go of it easily or not.

If there's one thing to this plan's credit, it's that it sure has done it's job as a distraction. It would have been impossible for Peridot to miss the commotion going down as two of her fellow supervisors fought their way through the crowded party, and as soon as she saw who was involved, sheer panic had driven her to follow. She'd haphazardly ducked and weaved her way past the other guests, leading up to this exact moment when she too spills out onto the balcony and into the rain, in time to see Gon accosting Sans.

If she knew ahead of time that this was planned, that this is all part of some design of Lambert's, she might think twice about doing what she does next. But she doesn't know. So she does what any sensible person with metal powers would do upon seeing two of her friends apparently trying to murder one another: She removes their weapons from the equation. Thwp. Both Lambert and Sans's swords are wrenched from their graps, and come soaring through the air to hover in front of the gem's outstretched palm.

She looks between both sides, utterly confused and dismayed.