Writing a good invitation/sponsorship letter for a visitor can take quite some effort.
It's important to include all needed information. There is no specific method, style or magic wording.
It's based on personal circumstances.
ECO's work to performance targets and quality procedures. Keep your invitation/sponsor letter concise and be sure all the required evidence is easily visible for the ECO.

Don't be complacent. Provide all the supporting evidential documents you possibly can.
Although refusal is not a disaster it's important that this first application represents your very best shot.

Focus on provision of sufficient funding and most importantly on leaving the ECO in no doubt she will return home.
It's always a fine balance but do give proof that the relationship is genuine and with a provable timeline. Do not divulge any form financial support you may have previously provided.
Give evidence of your visits to the Philippines and of contact over time. Emphasise the reasons why this visit is important at this time. Is your family aware of her? Do they welcome a visit from her etc etc
Then think carefully about all those genuine compelling reasons that really 'anchor' her within Philippines.
Just having material goods and some savings in the bank are not compelling reasons to return home in the mind of the ECO

Don't leave anything to chance and try to not leave obvious questions unanswered.

It's really a personal choice Whether or not you post your letter here in a public forum for comment.

The facts are whatever they are. No one here can magically come up with reasons to return home where there are none.

Just trying to help.