Moder was never intended to be a ground to air fight. She has set high ground spots around her spawn point that she lands on so you can attack her in melee. Trying to get her in the air is next to impossible since she isn't weak to piercing damage, just slashing.

just my view but the best thing for you to do might be to lure her back to her spawn point and fight her there. If you can't lure her use the devcommand to kill her using a "killall" followed by a "removedrops" so you don't accidentally pick up her drops and benifit from using the admin commands. Then return to her spawn point in the mountains and try again.

Something I found useful was digging under the edge of her summoning alter and placing a portal there then fill in any gaps between teh ground and alter with stone slabs. Stone flooring has more hit points than the natural stone and will take more hits for her to break. Getting 2 iron ingots up to her spawn point was one of hte most useful things I've done in the game. The portal give you a fast way to get back if you get killed and a way to leave if your HP gets too low. She won't regen her health as fast as you will.

Also recommend having a second portal a safe distance away in case everything goes FUBAR.

A second tip is have a AOE weapon like a stage breaker or Atleir, they break the ice crystals Moder's breath weapon makes and lets you move around better.

Hope some of this is uesful. Good luck.