Master's degree program(H4 --> F1 COS)

Hello,

My Fiancee is planning to start her master’s degree program after our wedding but she might not wait to enter the USA until she receives F1 Visa. we are planning to get her an H4, start her program and then switch to F1 status when we revisit India, which probably would be a year after our wedding(2 semesters into her degree). Are there any known issues that might arise when we try to apply for an F1 visa?

Only issue is as a F1 you have to prove non-immigrant intent. Note that H1B/H4 are considered dual intent visa.
Basically you will need to prove that as a F1 you have enough ties to your home country and that after completing your study you plan to go back to your home country.
That said, lot of people do change of status from H4 to F1 so there is no need to worry. When you apply for COS from H4 to F1 , hire a good immigration lawyer.