We gave our DS one from about 6 wks. He wanted to suck all the time (for comfort like your DD) so it was a lifesaver for me. It didn't interfere with BF at all. We also preferred that to thumbsucking. If his thumb drifted towards his mouth, we'd remove it and replace it with a dummy. Now, he only has it to sleep. We have to keep them out of reach during the day though because if he can get his hands on one, it'll be in his mouth & he cracks it if we take it away (that only lasts a moment though). He knows where we keep them too, he'll go to his nappy bag and search for one. We have to remember to take them out lol!