Actually, double sided tape doesn't really work as it lets go as soon as you start getting sweaty. Sorry. A strip of rubber is actually fairly affective, so long as you don't push it too far. Neither would work for BC.
The only real way to stick her costume in place is superglue. Hmm. That would make an interesting strip, if you pardon the pun...
most adhesives will simply dissolve exposed to sufficient warmth though.. in summer months that MIGHT get really really slippery, unless it's hyper-resistant, which'd make her have to take a bath in something really nasty, like acetone?, to take the costume off. /nerd off
This picture is well done and funny as hell. Still, I wouldn't recommend using tape to keep your costume from slipping. Your skin will hate you for that... dearly. Let's just assume her clothes stick to her body by free will because of her awesomeness!
There was a thing for a while wherein pretty much everyone's costumes but Grimm's were made of "unstable molecules" that kept them from being variously hampering or destroyed or whatever. Given the durability suggested and that the FF are pretty damn rich, I figured it being licensed out was a given.