Pike wasn't a Watcher. They were by nature cautious, and often unwilling to take deductive leaps until they've checked and re-checked every even potentially pertinent tome time and time again. He'd worked with hunters like that, and often found that attitude difficult in the extreme to deal with. Maybe it was because he didn't have regular access to huge wealths of occult lore, or maybe it was just because he lacked patience, but he found it a whole lot easier and quicker to work like a detective: Gather the facts, let them fall into the appropriate places, and make decisions based on your own observations, rather than what some old guy said in some dusty tome written two centuries ago.
So recognizing Leah wasn't as hard for him. She'd told him not to shoot a big wolf if he saw one. By itself, he might have just shrugged it off as an exotic pet. Thing was, that was only the case if you totally ignored the context of the conversation, which was killing supernatural things. It was possible that she had some kind of spirit wolf companion, but it was very unlikely that a spirit would have anything to fear from a gun, so she wouldn't have asked him not to shoot if that was the case. That meant whatever she was asking him not to shoot was physical. The context meant it wasn't a pet, and that it was very likely supernatural. Laid out like that, it didn't take a rocket scientist to figure out that she was either a werewolf or some kind of shapeshifter that liked turning into a big wolf. It was, theoretically, possible that she wasn't the only one here, but no one else except that vampire groupie girl had chimed in about the glittery vamps, so that didn't seem likely. It was a deductive leap for him to decide that the big wolf was Leah, but with the facts laid out like that, it wasn't much of one. Seemed an awful lot like common sense, when laid out the way he had it in his mind.
Fear never entered the equation. Maybe she could kill him, maybe she couldn't. Other things had tried and failed, both before hell, when he was still human, and after. He'd survived them all. And if he didn't survive Leah, so what? His entire life since meeting Buffy back in 1996 had been one giant game of craps. He knew it, and knew that inevitably, the dice were going to come up snake eyes some day. Death, his death, didn't scare him. It hadn't scared him since 1996. If it did, he wouldn't have been able to hack it as a monster hunter. Nowadays, not only did it not scare him, it didn't even bother him. He was a monster, and not just because he was a demon now. He was a killer, and it wasn't some tragic accident. He'd made the choice, he'd killed innocent people and heroes alike, and even when the Lord he'd been tortured into serving had died he'd just kept going. Demon or not, he was a monster, and what did the death of one pathetic monster matter, really?
It was why the snarl didn't bug him. It was why he didn't turn his head when she went off behind the bush. He wasn't sure whether she was shapeshifting back or setting up a pounce, and it didn't really matter to him. He'd been pretending to still be human, so chances were she'd underestimate his speed and reflexes by a decent margin. But he didn't think she would. She'd seemed fairly chill on the network, though of course anyone could seem chill on the internet.
Whatever she was doing, whether her intentions were peace or murder, he could wait. It was a nice night, and the lake was pretty, and right now no one was trying to kill him. It was a better night than he'd had in a long time.