Hi. Welcome to the Forum!!
I would advise to write a good covering letter from the sponsors highlighting the reason for your mum's visit and since your wedding will be next year she will have loads of time to settle all her papers regarding her properties (land title takes about three months to sort out; yearly land tax paid for the properties which is proof of abode etc). The land title should be available and really should have been sorted by now even if it's a notarized copy from the bank.
Show your Mum's savings account as well. As long as it is in a PH bank account it's one good reason for returning.
Any papers referring to her pension is good proof also, as she will need to return to be able to receive the outstanding amount.
Showing that she looks after her nieces, I think in this case is irrelevant as who will be looking after her whilst she is in UK?And if someone else is looking after whilst you Mum is in UK, then they could also look after her any other time, right?
The cold weather is also not a good excuse because us Pinoys are very adaptable at any age and coats and jackets are whole new fashion items we love to encounter.
I wouldn't bother to mention that your Mum is a pensioner and can't work here because some do, and they will know she is a pensioner when they review her documents.
Just try to be as factual as you can with the evidence of the funds; accommodation and the situation and also a real matter of fact covering letter stating that, as you have already gone through the visa application process yourself you, as a sponsor, realize the obligations, undertakings and responsibilities of sponsoring such a visa.
Good luck and have a beautiful family wedding.![]()