You aren't. Birds are even more susceptible to cigarette smoke than the other animals given their tiny lungs. Imagine you had a newborn baby in the house - would you feel OTT then? Nope. There's no difference - your pets rely on you to protect them and take care of them. You are their 'mummy' and shouldn't feel guilty for looking out for their best interests.
xx
Maybe apologise for being a little sharp with your friend (though I think she should not have just assumed it was ok to light up .... it's not very polite to do this without asking!) and explain the situation if you're concerned about hurt feelings. x