She's all for it!

"Of course, I would be interested in engaging with whatever Master and Princess desire," Virgo bowed her head, ever the picture of stoic servitude. "This is not the first time I have been asked to my Summoner's bed..."

"Huh? Then why are you called the Virgin?" Lisanna asked, stunned.

"It's more about her demeanor, she acts exactly as a virgin would, despite not being one," Lucy summed up as she groped Virgo from behind, making the spirit moan a bit. "Honestly, it's not surprising: obedient, sexy spirit in a maid uniform that obeys the orders of its owner, and always takes the most attractive form to them? Her being a literal virgin was not exactly plausible with how many owners she would have had..."

"That is correct," Virgo panted. "I hope this doesn't displease either of you..."

"Not at all," Natsu grinned as he and Lucy started working on undressing Virgo, leaving her maid frill on.

"...yeah, I guess that makes some sense... and I guess it gets points for irony too," Lisanna giggled.

Virgo stood almost completely naked and smiled softly. "I'm ready, Master, Princess," she stated. "Though, if I may, perhaps calling you Mistress would be more fitting now?" she asked Lucy, hoping to revert back to her original style of address with Lucy.

"Sounds good to me~!" Lucy grinned. "So, what should we do with you first?"