Tell her more

You attempt to stay on topic, digging deep for those college design classes you mostly slept through. If Ceilidh notices you're largely bullshitting, she doesn't seem to mind. Her blue eyes are heavy-hooded with desire and never leave you for a second. She reaches up and snaps off her hairband, leaving an avalanche of brown curls to tumble down around her shoulders, completely blocking out everything until her face is the only thing in your field of view.
Her shoulder twinge a bit and you look down to see her hand shoving all the way down her panties, sliding into her pussy with a lewd squelch. Ceilidh gives a fullmouthed moan and squirms against you. You only notice you've stopped speaking when she reminds you:

"Come on, stud.. Tell me.. Hnngh.. more about the golden ratio." Okay now you're know she's messing with you but at this point you don't mind. You've leaned slightly back in the chair and Ceilidh seems to have taken it as an invitation to move higher up your lap until you now feel her butt pressing against your erection, grinding against you whenever she shifts her pelvis to accommodate her fingers inside her. She grabs your hand and brings it to the buttons of her shirt, where she leaves it while biting her lip.
Taking the hint you start to unbutton her shirt and you quickly realize that she's not wearing a bra under it. You open the shirt and two small, pert breasts bounce free, large rosa nipples standing firmly to attention. You take them into your hands and Ceilidh mutters encouraging words, while you start massaging them, pinching her nipples between her fingers.

Her breath is ragged and you can tell she's getting closer. Her hand is now moving nonstop, rubbing her clit with three fingers while she leans forward to rest her forehead on your shoulder. Just as suddenly as she started, Ceilidh cums with a choked whine. She stops moving and you stop talking and for a second you just sit then. Then she gazes past you and perks up.
"Coffee's done!" She exclaims and hops quickly off your lap making her way over to the pot. You sit there dazed, not entirely sure what just happened. Ceilidh is still radiant as she once more drops down beside you, placing a mug of coffee for you and takes a sip of her own, but it seems like she has taken the edge off her lust and is now peering curiously at picture you've edited.

"So how do you know all this?" she asks, "don't think you've told me."

You're still not sure if telling you the truth would help, but on the other hand she did say her father was a reporter - maybe it will earn you some sympathy.