Applying for K1 whilst fiancee is studying in UK

I'm a UK citizen and am a software developer and my fiancee is studying forensic science to masters in the UK and living with myself, she will finish in 2020 and we plan to move to the USA ASAP and we're not the biggest fans of the UK culture. We are planning on starting the process of the K1 in Januarary 2020 so by the time graduation comes round hopefully the visa will be granted by the time of graduation approx september to october. Can we apply whilst we're both in the UK? To give reference we're both 20 years old at the time of writing. We obviously want to spend a minimal amount of time away from other and ideally both enter the USA on the same flight. Her parents have agreed to be sponsors for the visa. We have also been considering getting married and going down the marriage visa route (CR1) but this takes considerably longer than the K1 based on what I read. That is not ideal but with the K1 I am worried about how long the adjustment of status will take till I can work. Based on experience what's the best route for us to take? Many thanks in advance