Sorry if this has already been addressed, couldn`t find the search function to query this.
This works best if you are a range. Maghda will bubble every 25% of life lost and spawn adds. If you break the line of sight by running behind one of the pillars before she bubbles (before she hit 75% of her life), she will not spawn the adds and will not bubble. Repeat this for when she is about to hit 50% life and 25% life and you will be able to to kill her without dealing with the adds and her invulnerability bubble.