Carissa should be told that she needs 2x +6/+6/+4 headbands and 30 Wishes, where the second portion of those are for Keltham as part of a seduction plan she'll rederive next time she's fully augmented, but though Carissa shouldn't be told it during negotiations, you can step in and tell her it's really okay to settle at anything down to 1x +6/+6 and 10 Wishes, without which Carissa actually will walk out on them and see if she can become more valuable before selling.
(She leaves some space blank to add the justification for this, which she hasn't thought of yet at all.)