Ignore her and try to get Megumin's attention while also staring at Aqua's ass but ultimately get ignored/thought of as creepy by all three.
Make her wear cute frilly dresses, hold her hand in public and frequently loudly compliment her on how hard and heavy her muscled body is while calling her lalatina.
What kind of retarded name is DARKNESS anyway?
First, I'd make her wear a full-body latex bodysuit which goes up to the neck with holes in the places you would expect. Next, accessories, including an armbinder, a ball gag, a posture collar, nipple vibrators, a corset, and a nose hook. I'd also put vibrators in her pussy and asshole whose intensity I can control remotely. Similarly, in her urethra I'd make her wear a catheter with a valve that I can control remotely, ensuring that she only pees when I make her. On top of all of that, I'd make her wear a chastity belt that I hold the key to, so that no matter how much the vibrators stimulate her, she can't touch them or herself.
When she goes out adventuring as a crusader, I would only remove the armbinder, gag, and posture collar. She has to keep the rest on under her armor.