I can't figure out if your SO just hasn't thought this out,
Doesn't understand the difference between roomies and co-habiting?
Has thought it through, does understand but just isn't bothered?

It doesn't take a young, single, professional 3-5 months to find accommodation.(granted the cat may cause some issues.)
Legally, will you be able to make her leave once her time is up?
Is this really what you want for your first few months together?

Incidentally ,no she doesn't have to have equal parking privileges....your doing her a massive favour.

Family is entirely different. And what's concerning me is WHY is she finding it so hard to get accommodation?
Most companies who bring in out of state or foreign employees have recommendations for places to stay.

Dunno just feels...hinky.