**Sara Harvey and Bethany Young are sisters theory** (my theory may be similar to others')
I have no idea why Sara is in the cemetery (she is glancing at Emily) but there could be two possible reasons why she is there. First reason is, she could be sending her condolences to Emily's father Wayne Fields (his shocking and tragic death will occur in the time-jump) OR the second reason is, she could be visiting Bethany Young's grave and later encountered Emily. Hm I know you're wondering why on earth would she even visit Bethany Young's grave. Because there's a chance that she could be Bethany's sister! It would be a great twist if she is actually related to Bethany Young. Her motives would be avenging Charlotte and the Liars (including Mona) for her sister's anonymous death. She possibly wanted to involve herself in the A-team because she was willing to know more about Mona, the liars, and obviously Charlotte. Her main agenda is to be real close and friendly to them but in the end, she will turn out to be the main villain and threaten them because they were heavily involved in her sister's death. Remember Bethany is an extremely relevant character on the show because she pushed Marion off the roof in Radley, became close with Charlotte(big A), and she was falsely identified as Alison. Sara was surely present during "that night" when Bethany and Charlotte escaped Radley otherwise she wouldn't have been working for A. Sara might not be an irrelevant character (we all think she is because she's Black Widow and Red Coat with no apparent motives! Oh and she takes millions of showers a day like what?!) because Marlene confirmed that there is more to her story that will be revealed in 6B. Now I'm thinking this theory could be a good fit for Sara's background story as to why she decided to work for A but I don't think we will know why she kept on increasing the Fields' water bills. Anyways, in 6B, we might have a wider perspective about Sara being endgAme because she was 'the lady in black' and she sent the flowers to Bethany Young's parents. Whether we like it or not, the writers have already planned that Sara would be relevant on the show because in my opinion, I think she is Bethany's sister.
I don't think that something like that has been confirmed. But this is a fair assumption from YANNALPZ, as Wayne has already been diagnosed with something in season 5. Just can't remember what his it is. .
Cece and Bethany hated each other. I don't think Sara and Bethany were siblings, Sara was a 14 years old bitch from Courtland and Bethany was a 17 years old patient at Radley during September 2009. We don't know why Sara was helping Cece but I don't think this is connected to Bethany.