My "feeling" is that she herself put the status on "Busy", while she is not chatting with someone. This is just my feeling and based on my previous experience with some of Kasamba readers who always did this to pretend they are very popular.
There are a couple of reasons for that:
1. I monitored her activity several times, and refreshed the page non-stop for an hour and she's been always busy. Even when her local time is after midnight (once I did this from 7pm to 4am her timezone).
2. The times that she is actually busy, the "last seen" part appears on her page. Last seen shows the time she has started chatting with a client. But I don't see "last seen" most of the time on her page.
3. When I "search" her and her name shows up, a small green box shows up under her picture and says "online", however, when I click on it and goes to actual profile, it says "Busy". Again, the situation is different when she is chatting with someone. In that case, after search (before going to her profile page), the green box is red and says buys.
These are just my observations