i want to help but i don't know the new rules now. i used to be a student and was planning of extending my visa but obviously ur gf's situation is different as she has already extend hers.
when i tried applying for an extension, i found out that i can only extend if i enrol nqf level 6 in health and social care (this was early 2012). i am qualified but i find it too expensive. i didn't push through as i am only allowed to work 10 hours per week and must live in london coz my previous school is closed due to that clamping down of schools.
relationship doesn't base on how long u know each other. if it feels right then go for it. i met my husband a month before my visa expires. we're only in a relationship for 2 weeks when i left home.. believe me within 2 weeks of my stay in philippines, we already started gathering documents for my fiancee visa. yup, we both jump head first but we didn't regret it. we've had few downs but we are happily married.
whatever you decided, i wish you the best..