Looking for advice for my proposed spouse applying for uk visa, using visitor or tier 4 dependant?

I am currently on a tier 4 general student visa in UK as Indonesian (since 29 September 2018), and plan to stay in UK until 14 October 2019. So in my case, I'd like to invite my proposed spouse to come to stay with me until my departure date (bear in mind, as we havent married yet. We will marry at 7 April 2019 at Indonesia, I will go home first of course). After coming back to Indonesia for our marriage, I need to go back to London at 23 April 2019, as I will have exam at May. The problem is, I can't decide between two of the visa type:

For visitor visa

Pros:

• She can apply now (without marriage certificate)
• Cheaper (obviously)
• She can go to UK with me (this will be her first time traveling abroad, hence she will need guidance, her parents does not allow her to travel alone)

Cons:

• High probability of refusal because the proposed duration of her stay will be 5 months and 19-21 days (I know you can say like, "oh I will just say my stay will be in weeks, but in reality I will stay for months", but this is some kind of deception isnt it? I know you can try to explain for later visa application but I will try to avoid that)

For tier 4 dependants Pros:

• Higher probability of acceptance for the proposed duration

Cons:

• She will only be able to apply later after the marriage
• More expensive (need to pay full year for the visa and IHS, even though she will only stay with me for less than 6 months)
• She will travel alone, because visa decision may be after 23 April 2019 (dont even ask me to pay the priority service >_<)

The main problem is, she needs to travel with me, I already read lot of things, like how it is not good idea of using visitor visa for staying almost 6 months (especially for proving not to be overstayer etc), and even how you need a lot of relationship evidences (marriage certificate is not enough) to get the dependant route.

I am totally confused right now, any help will truly be appreciated.

Thank You!!

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Edit, for some more specific questions:

• For visitor visas, to prove the intention to leave (or the ties to home country), I will try to include 2 cases: -Our wedding party will be held after my study finishes, this will be proven by my fiancee's mother writing a letter asking her to come home -and my scholarship asked me to come home promptly after the study, proven by a letter from my scholarship (which because she will need to travel with me all time, she will have to be together with me too); Will these be enough for that?
• For the maintenance, I am using tier 4 dependant guidance (for visitor visa), which is 845/month x 6month= 5070 gbp, but because it will be a bit less (accommodation, flight, medical insurance are on me), will 3000-4000 be enough for that?
• If I will only use certificate of marriage, chat history, wedding ceremony photos, documentation etc for proving the subsisting relationship in tier 4 dependant visa, will that also be enough for that?