The answer is yes. Your sister can change her dependent visa status on college student if she is enrolled in a full-time course at the university or language school like YMCA.. Please be aware that to be accepted as a student you will definitely need to prove that you have enough funds to sponsor yourself whilst studying (one year in university is about 50,0000-70,0000 yen), plus if she pursues a Masters or PhD, she`ll have to pass an entrance examination which is usually held once/twice per year (September or February).

RAJDEB,

Your sister is the one who is having marital trouble and is looking for a way to stay in Japan on her own correct?

Note that to get a student visa she will need to have enough money to pay her tuition and living expenses BEFORE getting the visa. And she most likely will not be able to work enough while a student to support herself. This is not a very practical way of staying in Japan long term as it is very expensive.

I think those threads are talking about the same person. From what I gather, she has funds, a degree, but not much Japanese language proficiency...

RAJDEB,

If your sister has the funds and is interested in studying the Japanese language, she can find a Japanese language school, apply, get accepted, pay in tuition (she still needs to show that she has enough financial means to support herself without working), and through the school can apply for Pre-college visa status (most likely one year or two year programs at such schools, so probably she gets one year visa at a time).

The following are the four Japanese language schools that I've found off the website listing of Association for the Promotion of Japanese Language Education that are accredited to conduct courses to prepare non-Japanese students to study in the local language in the local universities in Japan.
http://www.nisshinkyo.org/MemberHome/B688-E.html
http://www.nisshinkyo.org/MemberHome/B654-E.html
http://www.nisshinkyo.org/MemberHome/B482-E.html
http://www.nisshinkyo.org/MemberHome/B459-E.html

I believe the schools I've listed above are the only ones in Utsunomiya city itself that are accredited to give "Precollege visa". (Not "Student" - those are for college/university students)

I don't understand your question. My understanding is that your sister wants to move AWAY from "Dependent" visa status. I am not saying that "pre-college visa" (the name is according to the Japanese government's immigration definition) is compulsory for anyone. But you say your sister "just needs to change her visa status," to WHICH status is she going to change?

If she applies for and attends a college/university, she can apply for "Student" visa. If she applies for and attends a Japanese language school, she can apply for "Pre-college" visa (someone correct me if I have the names wrong). If she finds a job in Japan on her own, she (or the employer) can apply for one of the work-permitting visa so she can stay and work in Japan for them.

Among those possibilities, I just thought that Pre-college visa might be the easiest, that's why I suggested that one.