Since that makes no sense, the only actual explanation is that Vaughn simply thought it would be funnier this way.
And Tilde's reaction is just a small part of what's problematic with the scene in which Eggsy has to seduce a woman so he can insert a tracking device into her vagina.
It's terrible in every way: outrageous, but not hilarious; nonsensical, but not even close to satirical; reprehensible and degrading, yet our hero's only hang-up is that he might piss off his possessive girlfriend.