Well, Margaret Hilda Roberts is the daughter of a grocer from Grantham, Alfred Roberts who is also a Methodist lay preacher so have him take a step up in the church and then packed off to the USA to support the Methodist church there.
Interestingly enough, the Methodist strongholds in the USA are Kentucky and Tennessee so the Roberts could actually drift towards the Democrat party rather than the Republicans, particularly during the 1930s and 1940s which would be an interesting development.
Roberts might apply to somewhere like Vasser or Brown, or might end up in a Methodist sponsored college. No need to mess around with the fact she studies chemistry though. If she graduates, she will probably end up in the growing petrochemical industry.
Roberts could become Thatcher - Denis was a small business man whose firm was taken over by Castrol Oil so entered the oil industry and the two could potentially meet. Or she could meet one George Herbert Walker Bush, who knows (although he married Barbara in 1945). Either way, there's every reason to think that (through her spouse and definitely through her father), she will drift into politics.
The rest, as they say, is history.