Light coloured females will not show vertical bars as far as I'm aware. You'll have to use her other body language as an indication of her submissiveness -- actions such as lowering her head and clamping her fins. These will be good indicators she's feeling submissive to the male. Also, good indicators that the male is feeling up to the task is him darting back and forth between the nest and the glass she's in. Aggressive behaviour is part of their mating ritual, but you do want to try and keep the female from being too hurt.
As a note, she may not show these submissive actions as long as she's safe in the glass -- you may need to let her out for a bit and let her get chased by the male. If he's built a substantial bubblenest, is darting back and forth from her to the nest, and she's full of eggs and seems interested, this is what I would do.
Hope this helps and best of luck with your spawning attempts! =)
C.G.