His girlfriend apparently rolled her eyes and called DD1 lazy and ungrateful when she said they missed me, told her that she smelled and asked the kids to move off the sofa if they ever tried to sit beside their dad
When you say English is not her first language, could that explain these things? I know that sounds patronising, but hanging on her specific words, when they might be less suitable than the ones a native English speaker might use, isn't fair.
I could be completely wrong of course. Only your DD was there. Do you think she was word for word told "you are lazy and ungrateful" or do you think it was "come on you haven't seen Dad for so long, be happy, not complain your mother is not here!"
My teen DS can definitely smell. Most teens can if they don't bathe every day. He came home from school yesterday, his last lesson was PE and he honked by the time he arrived home from the school bus. He walked through the door, and I said "Pooooooh! Bath for you!" He laughed and said "Yup!" Maybe the girlfriend thought your DD needed a bath? It's not beyond the realms of possibility that she did, especially if their dad isn't very hot on making sure they shower every day. So, the gf said as much, maybe not in a diplomatic way, less through intention, and again, more through language barriers.
And also, if DH and I are sitting down for the night, we have "our seats" on "our sofa" and if DS is (usually sprawled across both) sitting there, I will say, "come on, hoppit" and he gives me a very teenage look and moves to another sofa. Again, you'll know whether it's this, and they kept sitting in "their" seats, or if the girls were told to move no matter where they sat.
I worked with 2 Polish women. By the end of my employment, I thought they were two of the nicest, funniest, and kind hearted women I'd ever met. When I first met them, I thought they were rude, I'll mannered arseholes and I couldn't stand them. I remember the first time we went to a pub, and they ordered their drink, "one cola." No "hello, may I have...?" no "please" just a stern "one cola" as an instruction to the barman. 3 years of their English improving, and both them and I, understanding and making adjustments for the cultural differences between manners in the UK vs in Poland, made all the difference.