Through the generations the striping on White Tigers seems to be getting progressively fainter,(I'm not talking about the white stripeless tigers here) possibly either due to inbreeding or crossbreeding of races, I don't know which.
Look at photos of the original White Tigers at Rewa(India) Bristol or Washington Zoos-you'll see they were very boldly marked, quite unlike this female with her pale, almost fawn stripes.
I would suggest (off the top of my head) that Zena's brown stripes would primarily be explained by her being heterozygous for wide-band ('tabby'), being the daughter of a 'tabby' father Sonar and a white mother Chandi. I could be totally wrong, though!
I didn't realise she was the product of Tabby x White- that could well explain it. I do know nowadays there seems quite wide variation in the stripe colouration in White Tigers.