chris, here is the official website regarding student visas:
http://www.britainusa.com/visas/article ... 00&a=41074
If I recall correctly from my student visa days, she must show that she will be more or less self-sufficient (proof of funding, savings, etc), and should NOT have to rely on the part-time work to live. I also don't think it would be acceptable to use yourself as a sponsor, as that might show she doesn't intend on leaving after her studies (another requirement). If you decide to get married or switch to an unmarried partner visa while she is here, that requirement becomes irrelevent, of course.
And it sounds like a college course is acceptable, provided it is a full-time course (15+ hours a week).
Here are the all of the relevent requirements (cut from the above website):
To qualify for admission as a student, a person must:
* Have been accepted for a course of study in a bona fide private education institution (with properly maintained enrolment and attendance records), or an independent fee paying school outside the maintained sector, or a publicly funded institution of further/higher education*;
* Be able, and intend, to follow either a weekday full-time course attending a single institution for at least 15 hours of organized daytime study per week of a single subject(or directly related subjects), or a full-time course of study at an independent fee paying school, or recognized full-time degree course at a publicly funded institution of further/higher education;
* (if under 16yrs) be enrolled at an independent fee paying school on a full-time course of studies which meets the requirements of the Education Act 1944;
* be able to meet the costs of the course, accommodation and maintenance (including for dependents) without taking employment or engaging in business or having recourse to public funds;
* not intend to take employment or engage in business, except part-time or vacation work when given permission by the Department for Education and Employment, except see below “ Employment during periods of Study”;
* intend to leave the United Kingdom on completion of studies.
