It would probably help if you had another pair of hands to help you ;-) Never having done this myself, I would secure the cross in some way, and then carefully count out the number of ends needed for the project. Tie the 2 crosses separately and once you know that they are safely controlled, the original ties on the cross can be cut - get the extra helping hands to hold the crosses while carefully separating them into 2 warps. You will likely have to cut a thread at the other end to fully separate them.

If someone else has done this to a warp - maybe you could chime in with other ideas to help Diane!

Thanks Sandra but I think there may be an easier way to do this. The draft calls for weaving a 4" wide warp (each sachet's front and back are woven consecutively). Alternatively could weave a warp twice as wide (weaving fronts and backs side by side. Since my warp is already twice the desired width I wonder if I couldn't just cut the warp vertically in half once its off the loom and stitch the sides together after filling them with the lavender. see image attached.
Diane
https://ibb.co/9rHr2hG