The reduction could be due to either the amount of your private pension, or because the rules may treat your daughter as not occupying the property as she is not there in term time.
The Council should have given you a document showing how they have worked out your entitlement. If they have not done so they are at fault. You should contact them & ask for an explanation. If the reason is the first one I give above there will be nothing you can do, because the rules are national & the Council is just following them. If the reason is the second one, it may be questionable. I'm not sure about this, but there may be some case law which would help. So if the Council say you are only entitled to a one bed place I suggest you go to the local CAB & ask them for advice on whether this is correct.
In most areas getting a Council (or Housing Association) property involves a long wait - you should enquire of your Council Housing Dept. & get your name on their housing register. Council rents are often lower than those in the private rented sector; whether you would still get Housing Benefit would depend on the calculation based on all the factors, but it's likely you would get soem.