It does depend on the situation but there is usually a warm up period. When anyone walks up to anyone there is a period of wanting to know what is going on.
Imagine if the hottest woman or the oddest woman or the most average woman in the world started talking to you. How would you respond? Somebody talks about pacing the situation. They use it for a different purpose but the idea behind it applies here.
Let her adjust to what is happening. Let her determine what you want her to think is going on. In some situations you will have to do both sides of the conversation for a while.
Because there are so many factors that contribute to how long you could spend it's hard to give a specific time answer.
I think this might be a time to fall back on the idea that you are qualifying her. Once you have gotten a feel for what she is about she has probably figured out what she needs to know about you too. If she isn't warming at this point, move on.
Unless you want a pretty face attached to what you are essentially masturbating with. In that case try some of the seriously unethical SS stuff on her and see if that works.
