No this is not common among Histrionics! Im Have suffeed with HPD BUT never EVER, have a came on to a family member! She does sound like she suffers to, but it may be sex she is seeking, makes her eel loved, was she sexually abused as a child? I will look into this for you, but honestly Ive never heard of this type of behavior amongst family, the rest of her behavior lines right up though, have you told her about this site or thought about getting her coucleing?