No, Lisa was unaware that her brother had perished in the fight against Vandal Savage. She was not from such a far place in the time line to recall even being kidnapped by that horrible man. In a way it was a blessing Lisa remained blissfully unaware. If she knew she would have to face the rest of her life back home without Lenny, it would have destroyed her. For all her airs and ability to put on a good show, Lisa depended on her brother for a lot of things. He was her rock so to speak, her anchor, the one thing that could actually keep her semi-wild nature in check. Without him, Lisa could very well be a loose cannon of sorts.
"I always think of you," Lisa blurted. "There wasn't a moment that went by when you were sent back that I didn't think of you. I missed you so much, Lenny." It was a very real show of vulnerability for Lisa Snart, but the kind only brought out by her brother and no one else. At least, not yet. "But yes, let's hustle the wait staff shall we? Make it an adventure." Or a search party because she felt that was how Lenny was probably categorizing it in his mind at least.
Lisa stood, nodding towards the bar. "Order me something pretty, Lenny. You know what I like to drink." She gave him a small, playful smile before wandering back towards the kitchen where she promptly put her brother's order in for the best, most smashing cheeseburger the man could possibly cook up as well as a little threat to ensure he did just that. She put in an order for herself, but since this was a kind of his welcome back dinner, she made sure to emphasize she wanted Leonard's cooked first and no funny business about it. It had to be perfect because there was nothing less for her brother. "And make sure it's cooked properly. No raw meat. If it's not, I'll be back here so fast it will make your head spin." She did indeed add the last part with a wink to the cook who did look a bit frazzled at the encounter (proof Lisa did her job) before she headed back to the table, confident her brother had handled the bar.