Visitor Visa Advice

[Congypaul]

Hi all,
I'm new here and I'm not sure I'm posting in the right place but here goes.
I have been in a relationship with my Filipino girlfriend for over a year, I have visited her 3 times and on the recent visit ewe got engaged.
although we have talked about marriage we have decided the best route to take is a visitor visa so she can spend some time here building relationships with my family and finding out about our culture here, just a general feel for life in the UK.
My questions are firstly, although we have been in a relationship since November 2017 we Sony have any text /call records, we only have the last 3 months, that in itself is quite extensive as we video call maybe twice a day most days and sometimes for over 2 hours. We text constantly using what's app, but i used to regularly clear these chats as to keep space on my phone, would this cause us an issue in proving the length of the relationship? I do have a good collection of photos of us together on my visits and some with her family, they are just normal pics, no great holiday shots as when I'm there we are usually just spending time together out and about or at her family home. I have all my flight tickets from previous visits but I don't know if this is enough to justify the time line? Secondly my partner does have a job, she never asks me for anything so I only have one or two western union receipts and they are for very small amounts that I have sent as a gift so she can buy herself something. I know that having a job to go back to really helps with obtaining the visa but the problem is she only gets 5 days annual leave so that is just not long enough for a UK visit,she normally takes those days when i visit her. I'm wondering how best to approach this situation as her employer has already stated that any length of leave is out of the question, there is a possibility that her contact ends at the end of January and she will be offered a new contract, we are hoping that they will accept her leaving at the end of the contract and agreeing to her starting the new contract with a 3 week gap, but ewe are still waiting to find out about this.
My partner has 3 children which she obviously won't want to leave for long so we think a 2 - 3 week visit is enough and I'm also thinking that the kids maybe a sufficient reason for her not to over stay, also the fact that we intend to apply for a fiance visa in the future and would not want to jeopardise that. I'm a UK citizen and I meet the financial requirements for sponsorship, but I know these things are difficult to sort out and so much proof is needed. Any advice would be fantastic.

Thanks in advance

Paul