If she caught you in the act, do not ignore it, try to wrap it all into a joke, for example. Look at the situation. The simplest solution - to continue to look at other Russian women, but tell me, let's say you go with the Russian girl in one gym, or is it a girlfriend / wife of your colleagues, then immediately go to the next topic of discussion.
"Fool me once, shame on you, fooled twice - as I am not ashamed." Excuse of a gym or a Russian girl of your friend might work once. If you're caught in this again, you have to think fast. To focus attention on some of the details of the clothing of the Russian girl, ask she was not wearing it, etc.
Talking about your ex-girlfriend
The story about your former Russian girls - this is probably the most stupid thing you can do. In this case, you will be considered emotionally unstable person, revelers who does not notice him standing in front of a beautiful and charming girl.
The best solution would be an immediate end to this conversation. And do not come back to this topic. There is a possibility that the girl herself will insist on it, but do not need to do that. Even if you're in the middle of your explanations for the gap with another girl, immediately stop it by saying, "But nothing happened," and focus on that which is before you.
Switch to a different topic, and try to correct the negative impression, showing a naked girl interest in her.
You inadvertently insulted her
The first impression can ruin the most unpredictable things. Any your joke aimed at her, can cause trouble. Your dirty jokes about passing near the girl can be fatal if this girl was your sister a new friend.
If you're lucky, you're both just laugh good joke, but if not, you have to apologize. In both cases, the remaining time you spend on the threaded mitigating guilt.
The importance of first impressions
Although the first impression is important, it is rare to become the main elements of the "removal" girls. Everyone knows that you can not judge a person based only on the first few minutes of the meeting. Unsuccessful first impression can be corrected in the future you both can joke about it, remembering how it was.
Not every first impression is correct, but if you can fix it once, you will no longer worry about it.