Hi Dee...
As both an undergrad and a grad student at a "secular" university, I lived in coed dormitories. I think that the impression of "coed" dorms is often very misunderstood. Most coed dorms are merely apartments. No one walks around nude...or shares bathrooms/showers with members of the opposite sex. Rather, there are VERY strict rules about noise, appearance and civility.
I do understand your hesitation. Since every college and campus housing is different, I recommend that YOU & YOUR HUSBAND (and your daughter...but mostly, YOU & YOUR HUSBAND -- since the college will listen to you both more readily than a student) strongly protest this placement. Campus Housing (Residence Life, etc...) on most campuses actually are very keen to the living arrangements of students. If you express a "religious" opposition to this arrangement, the Campus Housing department will likely work very hard to make accomodations accordingly. However, you have to do this loudly, promptly (since space is limited) and often (like the "persistent widow").
You might also consider looking into the rules of this particular dorm. My sister-in-law was "stuck" in a freshmen coed dorm at Stanford this past year. It was actually VERY strict. Girls lived on one floor...where males were strictly prohibited without a staff escort. There were also very strict rules on noise, visitors, etc... -- which were more strict than most of the other "girl only" dorms.
By the way, most campuses have a waiting list for changing dorms. You might want to request to be placed on that list as soon as possible. However, I strongly suggest that you make a request for a dorm change if you have any hesitation (and make it sound VERY important to the Campus Housing office).
I will be praying for your family and this situation!
:-)
*EDIT - I disagree with the comments about "godless" colleges and universities. If your daughter desires to serve God as a medical doctor, she would have a difficult time obtaining admission to most schools if she attended a non-accredited school ("Christian" or otherwise) or if she received most of her education at a "community college." Most medical schools are very particular about who is accepted.
Also: As a person who obtained several degrees at "secular" universities, I was greatly blessed by God during my education. I fellowshipped with great Christian college students and professors. I was able to "pick and choose" the professors that I wanted (avoiding those "evolutionists" whenever possible). In fact, most of my undergraduate physics and chemistry professors were believers -- at a secular university. I was even able to take Bible classes taught by a Baptist minister (as a fulfillment of a "required elective") as an undergrad!
I do find the oft-repeated misperceptions of "secular" education to be quite perplexing! Colleges and universities are no more "godless institutions" than the regular workplace. Christian who want jobs usually have to work and interact with unbelievers. However, I not only thrived at "secular" universities -- I actually grew in the faith.
:-)