You ask her to betray the justice league

You smirk at the desperation in her voice, you could order her to do anything and while she may feel shame she would do it in a heartbeat. Just to be more like a proper fuckdoll.

You decided therefore to toy with Supergirl before bringing her directly in the fold. "Kara if you want bigger tits then there is one thing I want from you"

"What is it?" she begged, desperation growing in her voice.

"I want you to find every member of the Justice League secret identities, using your X-Ray vision and tell me" you ask.

"But I can't, I couldn't betray them" she pleaded, but the lack of sincerity and the overwhelming look of desire in her eyes gave her away.

"Well they keep interfering with the means of this process, and I can't continue the enhancement as long as they can conceal themselves with their secret identities. Unless you're okay with being flat chest?" you ask coyly.

The look of horror on her face was priceless "no I'll do it. I'll have them all in a week but I must have bigger tits, you have to promise" she begged.

"I will certainly think about it" you said preceding to have her risk everything on a mere hope of bigger tits.

"I'll have a list back in a week" she said shamefully, as she turned to leave you resisted from giving her a slap on the ass. Not wanting to provoke her yet, you would be patient. You had to wonder how the illustrous supergirl would react to the judas fetish you installed in her.