What is the difference between a Social Services Home worker and an Adult Protective Services worker?

In addition to what Alva said, think of it as Social Services can assess the situation and make recommendations where APS has the weight of the law to require action to be taken after assessing the situation.
In the case of your friend, know that unless the situation is severe, APS may not take action as soon as you think they should. Many times an elder must experience an event such as a fall that requires medical attention before appropriate action is taken. When that happens, it’s a good time to alert the hospital that your neighbor has no help in her home and needs to be placed. She may need emergency guardianship where the state steps in to manage her care. It’s a difficult situation. I’m sure she’s lucky to have you looking out for her.

Need to know your situation. Social services does one thing and APS does another. APS is responsible for assessing any situation where abuse of an at risk adult is concerned. While they may hold a social services degree it is quite irrelevant to the work really. APS will make a report to the appropriate authorities when there is a need for medical or social services followup. APS is a governmental service much like the police.