Should I list two sponsors for Short Stay Visa?

Hi all, thanks for the help. I will write a description of the situation first then list questions below:

My Indonesian girlfriend of 2 years is planning on visiting me in the UK this Christmas for 2.5 weeks. She is currently in the processes of applying for a short stay visa. She has her letter from employer, rent agreement, bank statements/payslips. She has less than £1,000 and a low salary but a reasonably good job in Indonesia, with good career prospects. She will be staying at my house in London for the whole time except 24th-26th December, when we will visit my parents. As a sponsor I am not ideal, I have £2,500 in my bank account, my rent agreement does not allow for couples (though they never would check). The only positive is my salary is now reasonable, although I have only been working for 4 months (just returned from 2 years in Indonesia).

Questions:

- Since my sponsor letter looks quite week, is it worth it to provide a second sponsor letter from my father, where she will be staying for 3 days of the holiday. He has a larger house, bank account and salary so would it lend greater credibility?

- Is there anything else she can include in her supplementary documents to increase her chances? She has family she would never want to leave permanently, and a few other work projects ongoing in Indonesia. She has only travelled to thailand before.

Thanks again!