If she's a seasoned model, it wouldn't be that. If she's new, possibly. As a seasoned model I'll still have a doozy thrown at me here and there but I can usually shrug it off in a few minutes and it doesn't make me cry. If I have a flood of bullshit assholes then yeah, it'll start to build. It very well may be (since she's Russian) its a studio OR the site is fucking with her money, she's onto it and getting frustrated (the ONLY thing that has made me cry on cam or log off to do so in the last year).
But, you said you asked and she shrugged it off so she obviously doesn't want you to know. Since she's your #5 you probably don't get as much from her as a long term consistent regular so she feels it was none of your business. ONLY my regulars that have been with me a very long time and have supported the fucking hell out of me get an honest answer to that question when it gets asked