I think savings are less of an issue than you're income allowing you to support her when she comes to the UK.
I would explain it on the covering letter, but very straightforwardly so it doesnt look like wheedling. You will need backup documentation, so payslips and bank statements are essential, and your bank statements hopefully can show a solid financial situation.
My biggest surprise here is how much you paid for flights to manila! I generally have been able to get flights for about £5-600 return!
