hi kabayan
I`ll take the liberty to answer your question but i`m hoping a senior memebr will give you a better insight to your sister`s situation.
There`s a long list of proofs in OP 2 Manual that your sister and her common law partner needs to submit for a common law sponsorship. I categorize them as hard evidence and sentimental evidence:
.Joint bank accounts and/or credit cards;
Joint ownership of residential property;
Joint residential leases;
Joint rental receipts;
Joint utilities accounts (electricity, gas, telephone);
Joint management of household expenditures;
Evidence of joint purchases, especially for household items;
Correspondence addressed to either or both parties at the same address;
Important documents of both parties show the same address, e.g., identification documents,
driver's licenses, insurance polices, etc.;
Shared responsibility for household management, household chores, etc.;
Evidence of children of one or both partners residing with the couple;
Telephone calls.
pictures together, with friends and family members
cards and letters written to each other but should be postmarked
text messages, emails, chat records
receipts of gifts such as jewelries, flowers, etc
letters of support from family and friends
I can`t say if they`re going to be refused but usually they should be prepared to go home to the Philippines for an interview if need be.
Is your sister`s partner also a nurse? I`m just asking because they can both apply under the Federal Skilled Worker. My sister in law`s visa only took 6 months to process from Manila. I believe if it`s a genuine relationship we have to fight for it.