[Tiva]

It wouldn't make you a bad mother but do realize that the smoke would still stick to your clothes, so you couldn't hold her right after smoking because you would need your clothes to air out. My sister has a 7th month old and it is what got her and her husband to stop smoking because Jackie isn't fond of the smoke smell even after they air out.
Also be aware of where your ventilation system is because it could draw the smoke back into your home and make her sick. It could in general compromise her health over all, asthma, SIDS, ear infections, and lower respiratory illnesses. That is just second hand smoke effects.
There was a study done back in 07 on how mothers who smoked and breastfed their children shortened their child's over all sleeping time. So another factor to add into your choice.

Over all I would not smoke once I had a child, at least until they were 15 years old (Fully mature in most areas of the body) but it is your choice just realize that they will love you no matter what but if they develop an illness because of your smoking they may resent your smoking latter on in life.