Sounds like she might be gravid, if she's showing sudden weight loss around the hips and tail base, reduced appetite and more digging behaviour.

You'll want a large area of deep dirt or a dirt/sand mixture, humid (but not wet) and compacted so that it will hold a burrow well, with temperatures below the surface of around 30C/86F. Put some large flat objects on the surface (thick pieces of plywood or large pieces of bark) to support the burrows once she digs under them.

I've never bred this species, so this is all based on what has worked for other breeders working with this and other monitor species.