Seat Reservations change Paris

Hello,

yesterday I’ve bought a seat reservation for a train ICE 9558 (Mannheim → Paris Est). I thought there’ll be an option to choose where I’d like to seat after pay, anyway it chose me random seat right in the couch 22. I’m travelling with my girlfriend who doesn’t have an Interrail pass, but every train I saw yet had an option to choose where exactly I’d like to seat.

When I tried to buy tickets for her on the https://bahn.com (Deutsche Bahn site) I wasn’t able to select the seat and the same for SNCF, they didn’t tell me the seat before I buy it. 

I’m afraid that if I buy two random seats and the train will be full, there’ll be no way to seat next to each other. Also, she’s getting sick when seated somewhere else than next to the window and in the direction of the travel. 

Is there anything I can do? Or at least can I refund my “random selected” ticket? The ticket (22/42) isn’t even in the direction of the travel as it seems from this only available plan of the couch https://www.vagonweb.cz/razeni/vlak.php?zeme=db&cislo=9558&rok=2023

Thanks everyone in advance for any help!