Are sleepovers at her place an option, or what about increasing the bed size by a little? Or is the bed already a tight squeeze with no room for anything bigger? If not, there are always options like Craigslist and Ebay. I do not know where you live, but beds usually have more than the standard sizes of Queen, King, etc. One off the top is the Olympic Queen/California Queen.
Outside of upgrading the bed size, I do not have any solutions. Glad all is going well for you!