Doesn't matter how many countries it is, the issue is getting the Schengen visa. If she has a full time job and other deep connections that will show the European embassy that she will come back, the visa isn't that hard to get.
If you just wear the backpack they almost never weigh it. They are more concerned with the bag fitting into the overhead compartment, which a regular backpack will do. So don't worry about it.
I think that, because visa agents are an actual real part of expat life in Thailand, until they give the whole immigration system a real overhaul, we should be able to discuss abd recommend agent services.
That way fewer people will get scammed by agents charging 400% more than others and and also learn what risks are involved in buying a visa through an agent. Sharing of information and real life experiences are a good thing 👌
Why are you flying to Thailand and then to Cambodia when there are direct flights into Cambodia? And why would you go through immigration if you're just transiting? None of this makes sense.