Castiel thinks over what she is saying carefully. When Anna comes close to him, there is a certain feeling of...exhilaration. His vessel's heart rate does increase and it only seems to occur with her. Other women have done so, whether it is simply the waitress at their usual diner or a student at the library from the local college, but he experiences nothing in their presence. As for the desire, he is aware that there is...something. He cannot define it, but each time she smiles at him or invades his personal space, there is a pleasant feeling associated with it.
"I...cannot say for certain," he admits truthfully. "Though I would be lying were I to say I've not experienced those symptoms often as of late."
Was that all love was? He doubts it, but clearly there is an association. He waits for Anna's assessment, knowing she would know what to make of it better than he would. "They...have been occurring increasingly often."