I would agree with the other moms and go. My best freind and I have a language barrier, and at first I worried if it would be too much trouble as well.
If not for anything else, do it for the kids. Finding good friends is really hard for kids, and if you don't help your daughter foster this friendship because you don't want to be "buddies" with the girl's mother, your daughter will feel the tension and might not hold on to a friendship that is good for both her and the other girl. Plus, it is a SMART idea to go over and really get to know how this other household works. Someday, if your daughter's friendship lasts with this girl- she will probably want to go over for sleepovers- kids parties- etc, and it would be kind of unfair to deny her if your only reason was that you didn't know the parents/household well enough, and you were unwilling to try.
Do you have to be best buds with this mom? No. But try to find your common ground - whatever it is. Chances are she just wants to know what kind of family her daughter's friend is around, and by taking the opportunity to get to know her, you'll both benefit, as well as your children. I have hung out with people that may not be my first choice in friends for the sake of my daughter plenty of times!
Good Luck!
-M.