As soon as you confirm the change from "attention" to "cock", you see a new hunger spark in Kelsey's eyes. She slides to the edge of the bed and, ignoring the open shades, begins unbuttoning her pants.
"Come on," she says impatiently. "Are we gonna fuck or what?" You don't need to be asked twice. You grab at your own pants, fumbling for a moment before you drop them and your boxers. Your cock springs free, already mostly erect and ready for action. Kelsey's eyes lock onto it and she leans forward, grabbing it in her hands and beginning to stroke it. You feel the heat and tightening as it swells from "mostly erect" to "fully erect", but before you can do anything Kelsey plunges her head down.
Her full lips envelop the head of your cock, and you gasp at the pleasurable sensation. Grabbing your phone, you quickly target yourself and generate a sentence.
"This girl is sucking your 7" cock."
Kelsey has begun bobbing her head along your cock, her tongue flicking across the most sensitive parts. With an effort, you force yourself past the distracting pleasure long enough to change "7" to "10" and click confirm.
"Mmf!" Kelsey exclaims, and you look down in time to see her mouth suddenly bulge with your expanded cock. From what you can see of the base of your shaft, it seems to have kept its proportions while growing longer. After her brief surprise, though, Kelsey renews the blowjob with vigor. She looks along the side of the shaft to the base, then back to the tip where she pulls you inside once more.
You were already near the edge from the earlier sentence you changed about yourself. Now, the sight and feel of Kelsey eagerly gobbling your cock is quickly pushing you over. Your free hand grabs the back of her head, entertwining in her blonde hair and pulling her deeper into each bob. She must be experienced, because she takes it without hesitation. A moment later, you feel yourself erupt into her mouth.
Feeling a little drained, you pull away from Kelsey. She's already swallowed your load, but as you slip free your cock lets out a last spurt of cum that splashes down onto her shirt.
"Oops," she giggles, licking her lips. "Guess I should have finished getting undressed first." She looks down at your cock, which is larger but still growing flaccid after your release. "Aw." Kelsey pouts. "Done already?"
"Sorry," you mumble. "I..." You trail off, looking at the phone. You could use the app to recover stamina instantly...you've already change Kelsey without her knowledge or consent. Do you really want to keep going?