Ooh! I love questions like this!
Okay, so this is actually pretty intricately tied to how I think her meeting with Blue would go. And it’s a little something like this:
Felldyne inhaled sharply and clamped a clawed hand over her (new) girlfriend’s shoulder. Alphys looked over at her, confused, and Felldyne drew her close. “Alphys,” Felldyne said slowly, “can we adopt a skeleton?”
The small, blue-clad skeleton across the field started waving excitedly as soon as he saw them. Stars—actual stars!—danced in his sockets and he grinned broadly, obviously delighted to see them. “…didn’t you already adopt a skeleton?” Alphys asked, earning a glare from Edge.
“Yeah, but he’s an asshole!” That earned a growl. “This one’s adorable!”
“Careful,” Edge cautioned, still glaring at both of them. “He’s already got an overprotective reptile breathing down his neck. He doesn’t require an overprotective fish as well.”
“Huh?” Then Felldyne saw a battle-scarred lizard monster approach the smaller skeleton, chatting amicably. She was short and heavily muscled, and missing one eye. Felldyne grinned and rolled her head and shoulders. Loosening up. “I can take her.”
“Undyne. No.”
“HEY! THUNDER THIGHS! YEAH, I’M TALKING TO YOU! LET’S DO THIS!”
Edge sighed and massaged the ridge of bone between his sockets as Felldyne and Swaphys ran toward each other, both of them shouting. “I knew this was a bad idea.”