BUT NOW SHE HAS CHANGED SHE JUST SAYS HELLO AND DONT SMILE AND REALLY DONT WANT TO TALK. WOULD IT BE A GOOD IDEA TO BUY A GIFT TO SAY SORRY OR SHOULD I JUST LEAVE IT CAN ANYONE HELP
Leave it as it is!
Especially, don't buy her gifts because it'll make things even worse and questionable.
Anyway, why do you feel you need to buy her gift??
Your Polish lady co-worker and her husband probably don't want to keep any closer relation with you. Maybe her husband doesn't like you to be her friend instead of a co-worker.
On the other hand, that's normal Polish behaviour, some couples like to keep to themselve only.