I bet Hilda would get along with Isidro and Schierke, even though they're a bit older than her. And probably Guts, given his fair track record with small girls after the Eclipse. ('bout 50/50) Hilda would love Puck, but I bet he'd drive Alfur insane.
I once requested crossover art of Hilda and Berserk, actually. Just a sketch, but it came out great. Sadly I cannot post it here, as it involves Berserk trolls which are decidedly less courteous than the Hilda version. Still it may be the only crossover art between those two series that exists.