Dementia is difficult for everyone involved. The early stages can be particularly perplexing; your loved one still appears her old self most of the time, but then suddenly she will
say something completely off the wall. The symptoms of memory-loss and confusion fluctuate and in the early stages they can be very sporadic, so it's easy to think that she's faking her dementia.
She doesn't want to accept her impairment and neither do you. Consequently this can be a particularly lonely period for her, as she's feeling more and more alienated from the rest of you. What's further confusing for everyone, is that she's likely still able to "keep up appearances." She can resort to platitudes to keep a phone conversation going. The person on the other end is blissfully unaware that she'll retain little of the conversation.
These days it's more common than not that families live apart, in different cities or states. Since the person with early stage dementia will still sound reasonably normal over the phone, the distant family-members can easily assume that the local fulltime caregiver is mistaken is her interpretation of the loved one's mental state. This often leads to disagreements and conflicts. Ideally everyone in the family should take the opportunity to spend real time with their loved-one in her familiar environment. This will help to get everyone on the same page to support each other. These long visits will also give the fulltime caregiver a much-needed respite.