You shouldn't feed into it at all. It's a stereo type. Back in my home town, the hispanics are the only ones working construction right now. Not because the "white people" don't want to but because the economy is so bad no one wants to pay full price and the hispanics are willing to do it for much cheaper. My Grandfather owns a once VERY successful masonry company. But now he can't get any work at all because no one is willing to pay full price any more.
Your friend did stereotype you and it was wrong. Lots of "white" people have worked construction. I was working construction with my dad when I was growing up and would visit him and my brother and mom (when she got off work from her desk job) worked in a warehouse for years before he joined the Army, same as my husband.
Just don't listen to it. It will only make you upset and people who love to think in stereotypes will never learn so there really is no point in even speaking to them about it. You can however if you feel compelled to just tell her you didn't appreciate her saying that, it wont change her view but at least she might not say things like that around you any more