I doubt that there is much physically wrong with your daughter, but it is better to get her checked out just to be sure.

Mentally though, you may have inadvertantly started her on the path to being afraid of dogs just by the way you reacted to the situation.  Your reaction could have made her think that dogs are something to be afraid of, and she might end up being afraid of all dogs, or just large dogs, further down the tract.

To stop that, you need to have and she needs to have, positive interactions with dogs so she can see that they aren't something to be afraid of.  You should also teach her the correct way to approach a dog.  If you want some advice on that, just ask- animals and the way they behave is one area that I'm pretty cluey in.

As for feral kids, we got 5 here too, but at least they aren't that bad- ours just like a lot of noise (their own voices preferably), getting into mischief and driving us parents up the wall! lol.  We would never let them behave like those kids though, and certainly wouldn't let them pick up our baby (though they do if they think they can get away with it- thing is, bubs loves it).  I really think that the parents are quite lacking in some skills, like providing a safe, supervised environment.  It sounds like your girls are a bit more controlled in their behaviour, which just goes to show how much time you put into actually looking out for them.  Not saying the other mum isn't a good mum, just sounds like she is more 'casual' in her approach, and it probably works for her.

Wow... I bet you won't be going back there in a hurry! If it is really worrying you, take her to the hospital. Even if its just for your peace of mind. Hope she feels better soon :)

With head injuries, you need to look out for vomiting, drowsiness or sleepiness, confusion (if she says strange things that don't make sense or isn't sure wher she is), irritability, dizziness (either by what your daughter can tell you or watching her gait/walking style).  If she develops any of these problems you need to take her to the emergency department.  Only you can see what she is really like so I can't recommend you taking her or not at this stage.  If you are thinking the hospital option because you are still concerned then its better to be safe than sorry.  Mother's instincts are usually right.  You are lucky the dog was only being playful, a bite could have been much more serious.  She will probably have a headache, so some paracetamol might be in order.  hope she feels better soon.

for me i would think its just a bruise keep an eye on her though we all know the damage kids do to themselves at the same time keep an eye on her i'm no doctor  BUT i wouldnt be going there again doesnt sound to good .If you dont want to break up the friendship have the other child at yuor house

wow!  What a stressful place to go for a play!!! 

If it's bothering her then yes, take her toa  doctor.  If you choose not to then just watch her anything out of the ordinary.  with lumps on kids' heads, do NOT put ice on them to reduce swelling as this might cause the swelling to internalise, which may in turn put pressure on the brain.  When I did first aid (in prep to work in day care) we were given that advice and I am pretty sure it is still current but maybe you could ring your local ambulance station and check with them.

I personally wouldn't be going back there though as it sounds like the mother has no control and I wouldn't want my daughter to start behaving like her friend.