The police are bombarded with calls about anti-social behaviour - the PSNI will prioritise calls just as any other police force (e.g. the Gardai) will - the police are massively stretched and under resourced at the minute (I ran this past a PSNI constable friend of mine).
This doesn't sound like just "anti-social behaviour". Anti social behaviour is a couple of louts drinking on a street garden lobbing bottles. Your daughter has been assaulted. Take her down the station, give a full account of what has happened / is happening, and then see what happens. If you're still ignored then by all means give off stink about political policing/bring the Provos in etc etc - however for now I think you're bringing in an unnecessary and unwarranted political element to the situation that, in all likelyhood (on the PSNI's part) doesn't exist.
As a nordy Im embarrassed that this sort of thing is happening (in terms of the abuse dished out to you and your daughter) - it seems to be a wider society issue in that scum will pick on anything that marks you out as "different" - in this case its because you're an outsider and from the south. Portadown has been reknowned for its attacks on any outsider (eastern europeans in particular) and is one of the towns in NI where sectarian scars run very deep in what is a minority of people. Unfortunately you only need to live within range of a couple of eejits to make you're life hell.
Keep us posted with how you get on anyway.