Dry eye seems like the most likely issue, which can cause glare and halos, but I'm not sure if I'd seen it mentioned as causing rainbows and halos. I know there are a number of other causes for such things, I'll let the doctor or others comment on them since I hadn't looked into it.
Since a quick check of your profile shows you say you are 16, if thats accurate then the odds are very low its a cataract. In theory its possible, they can happen at any age, but mostly it would be due to some risk factor you would be aware of, like if you've had some sort of eye trauma or had to take steroids for some other condition.
I'll note that at least glare issues are common (whether they indicate a problem of concern I'll let the doctor or others address), this mentions their frequency
http://www.envisionmagazine.ca/special-contact-lenses-can-help-avoid-car-accidents/
"The study, titled Needs, Symptoms, Incidence, Global Eye Health Trends (NSIGHT), surveyed 3,800 spectacle and contact lens-corrected subjects, 15 to 65 years of age, from seven countries (China, Korea, Japan, France, Italy, United Kingdom and the U.S.) to better understand the eye-related symptoms that vision-corrected patients experience. The NSIGHT data provided valuable information on how often patients experience halos and glare and the degree to which they found them bothersome.
About half of the spectacle and contact lens wearers surveyed reported suffering from the symptoms of halos (52 per cent and 56 per cent, respectively) and glare (47 per cent and 50 per cent, respectively) more than three times a week. More than four of five patients who experienced these symptoms found them bothersome (84 per cent and 89 per cent for halo and glare, respectively). "
I will note for the benefit of others who might read the thread, that cataracts vary quite a bit in how quickly they develop, its merely that at her age its unlikely. It is possible to have a problem cataract appear even if someone had a checkup a year ago (though its very unlikely in your case). Normal age related cataracts usually take many years to develop, and the average cataract surgery patient is in their 70s. However eye trauma and other non-age related causes may cause them to develop more rapidly. In my case I had no risk factors, so it may have been merely a very early age related cataract (even 49 being very early for it), and yet the cataract only took 3.5 months to bring best corrected vision from 20/25 down to 20/60 in that eye. (I was trying new contacts, which is why in followups the optometrist noticed something was changing quickly).