What is the point of this quote in Between Shades of Gray?: "Mrs. Arvydas turned her head to me. Her eye make-up ran down over a bloody welt that blazed across her cheek."

I think what this quotation does is highlight something about Mrs. Arvydas's predicament in the forced labor camp. Mrs. Arvydas is a very attractive woman who's been sleeping with officers of the NKVD—the Stalinist secret police—to save herself and her son, Andrius. Although this keeps her and Andrius alive, it does little for her dignity and self-respect.
The NKVD officers who sexually exploit Mrs. Arvydas clearly have no respect for her, and even though they spare her the ultimate fate, they're not averse to beating her, which would explain the bloody welt across her cheek. It's obvious that these men have no respect for Mrs. Arvydas, treating her as little better than a prostitute. And yet she has no choice but to degrade herself like this each and every day if she and her son are to survive the horrors of a Siberian labor camp.