Jolene maintained her smiling appearance while Lex spoke, and did not show any changes, keeping her thoughts hidden. Naturally, such a thing was completely ineffective against Lex. Not only did he have his sixth sense giving him feedback, his intuition was also providing him with a sense of what she was feeling. Moreover, after confirming with his intuition that it was safe, he conducted a little experiment with his soul sense.
He used it to observe any fluctuations in Jolene's soul. Lex could not observe in too much detail, as she would likely sense something amiss even without a soul sense of her own, but it was enough to simply observe from afar.
Although her thoughts did not cause any prominent changes to her soul, Lex could clearly determine that she was in an excited yet tense state. Basically, she knew she had stumbled across an opportunity, but also knew that she had to be cautious to make use of it.