Ok, your fiancee won't apply for a spousal visa. She'll be a dependent on your student visa (unless you're a UK citizen?). So, you need to apply for your student visa after you get married and she'll be a part of your application. You can get your visa on the same day if you travel to the consulate. I don't think you can amend a student visa to include your fiancee after the wedding. Just wait until after you're married and have your marriage certificate. It won't be suspicious. You planned a wedding, she's legitimately your wife. And if you apply for your visa on say, the 14th of August, I'm sure you'd have it by 6 Sept. Student visas don't take that long to process. Mine took 12 working days.