Depending on what lender you go to, that could be an issue. But for many lenders like my company, we don't have any minimum open or reporting tradelines for an FHA loan. In fact we don't even need all 3 scores. With a 600+ scores you should be good. If you want to get a additional credit card for her, that would be fine, just make sure she doesn't miss any payments! It's been my experience that you want the quickest point boost, make sure she charges up to but no over the credit limit. Meaning if the card has a $300.00 credit limit, charge $250.00 or so. Then pay the account 5 days before the statement cutoff date or statements posts. Make sure the statement reflects a balance of 7-10%. Near let it post over 30% or near pay it to zero. Hope this helps you.