Corrected entry: As long as Elsa had the gloves, there was no need to keep her away from Anna. I know her powers were still noticeable with them, but she couldn't harm Anna with them. The point of keeping her away from Anna was to protect her.
MikeH
2nd Nov 2017
Correction: The gloves did nothing besides calming (sort of) Elsa with their presence. They were completely placebo, they merely helped her think her powers couldn't seep through so she never got scared enough to set her powers off while wearing her gloves. Remember, she froze the water with a tap of her foot, so her shoes didn't hold her powers back either.