Hi Christina
As someone who flies most weeks, let me tell you that I don't really care what size you are, what colour you are or anything else :-)
If you are good at you job that's great and if you are pleasant, that's a bonus. Most of us are so pressured with work that we usually don't remember the good check in agents, which sounds rude, but it isn't because it means that they did their job well and we could devote our attention to the problems that we need to deal with.
You are, understandably, concerned about this but from a pax perspective its a non issue.
mfg