Frisk's first response was, instead of answering her question, to go, "Ah, so you're the one who was the succubus monster thing they mentioned. Unicorn like Twilight too, and from that pony world. Wonder where the Sunset Shimmer of this world is." Then shaking their head, Frisk shrugged and pointed between themself and Asriel.
"We've both got magic too. Asriel probably more than anyone besides you, I wager. When I met Twilight, I flirted with her, as I tend to do with all pretty girls. Speaking of which," And here they gave the trademark Frisk charm, "With you around, I don't think I'll ever need to wait to see the beauty of a setting sun~"
Spoiler (click to show/hide):
Charm roll of 16 on the dot lol
Continuing on, Frisk finished, "When I pointed out Twilight's shirt was see through and showing her nipples after I pulled her from the fountain she fell in, I don't know, I guess my magic interacted with her and PUT her in heat? CHECK told me she was in estrus after all."