She could just be trying to warn your DD to stay away from her, but she needs to know that it is NOT ok to exhibit that behaviour in case it does escalate. Better to nip it in the bud from the very beginning of the warning. Get a good trainer and start teaching your DD that your dog doesn't always want her close to her. I know it's hard with a 13 month old...maybe get some baby gates and section of an area of the house for your dog to go? I wouldn't be reassuring the dog that it's "ok", she'll just think she is being rewarded for the behaviour (same principle for dogs that are scared of loud noises etc. If you pat and reassure them it's only reinforcing the behaviour they are showing). You're better off rewarding her when she doesn't growl at your DD.