I would dip the whole plant outside in a 5 gallon bucket with sevin and water.
available at your local lawn & garden store.........keep the whole container in this mix including the flower until the bubbles stop..................take the plant out......change the soil and new pot................tape very carefully the roots to get the dirt off or use a pencil....now dip that root in the sevin liquid several times gently to get most of the dirt off.......now replant that in new pot same size and new house soil.....don't use soil from the $dollar store because it is not baked to kill mold & spores and bugs.........so let it sit in the shade for a few minutes while you get rid of the mess in the trash...don't use that soil anywhere it has mold in it. and you can dump or use that sevin mix that day on any outside plants that are not edible....................keep children and pets away from that mix. I wear old long clothes when working with any chemical, including gloves, goggles and mask. Check where ever you had that plant and see if there is anything in another plant before you dump that mix................you might be over watering......you might need to get one of those soil humidity testers.