we have to pay half rent and council tax because they class it as income, so we are worse off basically,
How are you both worse off? As your partner has now moved in with you, you now only one set of household bills to pay.
Council Tax Benefit has ended and been replaced with Council Tax Support, which means you would have to pay some towards your council tax bill anyway even if your partner wasn't living with you. Each council sets their own level that a claimant has to pay and this amount would have risen again in April 2014.
You also lost your 25% single person council tax discount your partner moved in with you which have increased your council tax bill.
Have you informed Tax Credits that your partner is now living with you and changed to a joint claim? Your other benefits will not be affected by her moving in.
What my thought was, when you claim uk disability you can still work, so wouldn't she be able to claim UK and keep usa to as they already class it as an income? she would only get the lower rate UK im sure but it would mean she was then classed as disabled and i would hope we would get a little extra help with the rent and council tax.
Disability (DLA) has been replaced by PIP now. However under PIP, the lower amount of disability has been removed. From what you say, it seems that she wouldn't be given PIP?
Being disabled won't get extra help with Housing Benefit or Council Tax Support because, as you said, those who claim DLA/PIP can also work as it's not an income based benefit. The money from DLA/PIP is to help with the extra costs of being disabled.
As to whether her US disabilty should be counted as income for your Housing Benefit claim, try asking on
www.moneysavingexpert.com on the benefits board, as they have housing benefit staff posting on there.