I strongly agree with K M. We would all be surprised at what our babies swallow. Everything they touch goes into their mouth. Hair will go thru her digestive track without any difficulty. Perhaps the baby who became constipated had swallowed a large clump of hair. Perhaps the clump of hair after someone had cleaned out the hairbrush after several weeks/months. It would have to be enough hair to completely block her intestines. Getting that much hair from crawling on the floor and picking up a hair or two on her fingers is not going to hurt her.
We are all loosing hair everyday, one or two hairs at a time throughout the day. You cannot clean your floor so that there is never a hair on it. Since it's been hot I've been running my fingers thru my hair when I'm on the computer. In an hours time I can see several hairs on the keyboard.
Our bodies build up immunity by being exposed to germs. I do wonder how this next generation is going to fare with all the emphasis on anti-bacterial everything.
My daughter's sister is a super clean freak. She even shampoos her rug every week or every other week at least. Her kids are frequently ill. My daughter, who has kids the same age has not shampooed her rug since she moved in 5 years ago. The only anti-bacterial product she uses in hand soap. Her kids are healthier.
I've seen my grandchildren, as babies, pick up lint and assorted other fluff off the floor. Usually they don't like the texture and spit it out. It's quite likely that your daughter isn't aware that there is a hair on her finger. Which reinforces the idea that she is swallowing very little hair.
Anything that we swallow passes thru out system in 24 hours or less. Therefore she has no build up of hair in her system.
Look at cats who swallow lots of hair as they groom themselves. I frequently find long clumps of hair on the floor and in the yard. Sometimes cats get a hairball which causes them to cough and gag. The hair always comes out of one end or the other.
Please just relax. Kids are tough. And why worry about something that might happen? You've seen no ill effects so far. Why would there be ill effects in the future?