The college most likely has a counseling center that she can go to for free treatment. If she is attending college out of state, you may phone your insurance company to find out if she would need a "guest membership" while away or not. The ins can also give you in network referrals.
As long as she is willing to get help, she can work with any clinician such as: counselor/therapist, social worker or a psychologist. A psychiatrist will be someone who would generally prescribe medication such as antianxiety medication. Her frequent urination may be related to high anxiety levels as well as other causes i.e over active bladder, Interstitial cystitis, kidney stones, diabetes, etc.
If the urination is connected to her anxiety, she can work with a cognitive behavioral therapist. Usually this involves goal oriented short term treatment that would address what is behind her anxiety and how to manage her symptoms.
If she's noticed that the frequent urination occurs even when she is not anxious/stressed out, she can have her GP check for medical causes for it. Her GP is another person who can prescribe anti anxiety medication if your daughter wants to try that option. There are also medications that for the time being can help control her frequent need to urinate such as Vesicare, Oxybutin, Gellnique patch, Toviaz, etc.