For me just as important as bank statments is your cover letter which shows that everything is in hand when your both back in the UK. The bit which many forget.
Examples are.
Food bill will rise far more than for a british partner due to possibly wanting foods which are more expensive in the UK. Indicating you realise this helps show you are taking this seriously.
Leccy/gas bill may rise a tad more expecially in the first winter.
A entire wardrobe will need to be bought for the three seasons your mahal will never likely have experienced in her life. Plus if like my wife who was in her very early 20's she found the style of clothes in the UK so different even her summer clothes she wanted to change a little to fit in.
Phone bill may raise she will need to contact more people in phill than just you who may not be able to use computer normally the cheapest or landline, but mobile which is normally a few pence a mintue more expensive on the cheapest rates.
Also transport your Mahal will most likely if your at work all day want to get about which will mean bus/train fares and of course a little spending money.
So you take note of the actual costs which will increase, let the ECO know its all under control and has been discussed between the two of you.
Ok some are estimates but sound like you are serious.
It doesn't take much more time when preparing to do but makes you feel you have ticked every box while waiting which you will find is important as the why didn't we do that say this write that comes to the fore in application waiting time