My sister flew to Shenzhen on 10th August to visit her friend, She intends to stay there for another 1 month, can I help her to apply the visa in singapore ?

Dear Sir / Mdm ,

Need your kind help to advise .My sister flew to Shenzhen on 10th August to visit her friend . She intends to stay there for another 1 month .

1)Can I help her to apply the visa in singapore ?
2)What are the documents I need to provide ?
3)Can I apply online ?
4)If all the above non-applicable , where can she apply in Shenzhen ?

Thank you very much .

Hazel