Surprise
Chloe hadn't blinked at Lex's eagerness to help with Clark's birthday party. That's the sort of things friends do.
She realized Lex wasn't your typical friend; so she'd tried to take his enthusiastic flinging of money, his over-the-top offers in stride. Fireworks? Coldplay? Sure, Lex, thanks.
The real shock came, not with springing out of hiding and yelling "SURPRISE!," but upon arriving at the barn the day of the party.
Lex had been supposed to ambush Clark, take him somewhere, distract him so Chloe could decorate and finalize.
That kiss certainly looked distracting … but it wasn't exactly what she'd envisioned.