Fleas are crazy bad this WINTER
. I went through this just a few weeks ago. Be oh so careful with your baby and sprays etc. inside the house, she is very young. Dawn dish washing liquid works very well, but it is also very drying for their skin, use a good conditioner. With her being so young and tiny when you soap her up wrap her in a warm towel for the 5 mins the vet told you to keep her soaped, they can get sick with sore throats etc.
Treat your yard and hit it hard, and in 3-4 weeks hit it again. It is extremely important to treat your yard! As far as inside the house vacuum everything, floors, couch, chairs under furniture etc, then empty the canister or bag and get it out of your house. Wash everything that you can, bedding, blankets, pillows, etc. I also shampooed the carpet in the bedrooms. This is almost a daily process until they are gone.
I feel for you, I am just coming through it and it seemed like it happened over night and it was an invasion of the fleas
. BTW Front Line is useless anymore, I had just put Front Line on mine right before the fleas showed up. Apparently fleas are no longer responding to it, at least not SC fleas
I HATE fleas, have never had a problem before and flipped out when I seen them. Just please be very, very careful with such a young baby, they are sensitive to so many things and my husbands brother treated his small poodles bed with flea spray and it killed her (YEARS AGO).
Good luck! Others will likely share more advice that will be helpful too!