First of all, know that by and large medical students are insecure jerks and that you should ignore any and all advice from them. Their own insecurity will not allow them to see you comfortable in a difficult situation. It is highly likely that things will work out well for you, especially if you are willing to apply to a couple of different specialties.
Second, know that it is exceedingly unlikely that two clinicians in different fields will randomly strike up a conversation about residency applications AND that your name will come up in that conversation AND that it will be seen as a negative that you want to train with your significant other. Students think that program directors etc. care a lot more about who trains there than they actually do. Simply put, no attending is going to lose sleep about a single candidate one way or the other. There are just too many other things to occupy their time (wages, malpractice, academic pressures and so on).
Third, if you are willing to consider more than one specialty your likelihood of matching may increase rather than decrease. Residency interview committees are made of people, people have difficult situations they deal with and most carry some empathy with them because of it. All you need to do is whatever you can do to ingratiate yourself with the people who will make the decisions in whatever field/fields you are considering, work as hard as you can in every rotation you do, be a good, caring, nice and considerate person and things will likely work out in your favor. It is much MUCH MUCH more likely that two attendings will discuss the pleasant hard working student on their service than they will discuss a person in a difficult situation who is trying to make the best of it.
Finally, to reiterate, DO NOT LISTEN TO MEDICAL STUDENTS ON MATTERS LIKE THIS, THEY DO NOT KNOW WHAT THEY ARE TALKING ABOUT.
Best of luck,
jdubya