Her symptoms are very suspicious of a condition called cognitive dysfunction syndrome. It is a condition that we see in older dogs with signs that vary from dog to dog. For lack of a better comparison, it is similar to Alzheimer's disease in humans. IN the early stages, the signs can be difficult to recognize, but as it progresses, is usually much more obvious.
I am including an information sheet about it for you as well as a checklist for you to use with your veterinarian.
CDS checklist - this is a checklist used to help owners chart the progress of treatment if they treat with meds, but it does list of the signs.
maturedogs.com - This is also a website devoted to older dogs and has a whole section about CDS.
Here are some of the most common signs seen, but there are many others as well:
general confusion - your pet doesn't greet or seem to recognize you as before, your pet gets 'lost' in the yard or house
inappropriate vocalization - barking or meowing in the middle of the night, or for no 'good' reason? (I know, some dogs don't need a reason to bark.)
getting day and night mixed up - sleeping all day, awake all night?
confusing indoor and outdoor - a previously housebroken pet soiling in the house?
personality changes - i.e. a formerly outgoing pet becoming timid or aggressive?
I have seen a good number of dogs affected by this and all have exhibited different signs, especially in the early stages. Some dogs I have seen have responded to diet change alone. Hill's b/d diet is a good choice. If not, the medication called Anipryl® is very effective for many dogs.
I generally start with the supplements first (+/- diet change to b/d if there are no other dietary restrictions needed). I usually recommend increasing the omega 3's in the diet as well. The active ingredient of fish oil is EPA (Eicosapentaenoic Acid) and DHA (Docosahexaenoic Acid). You just want to make sure you are seeing those on the label as an ingredient and not just the words "fish oil" as these are the important part of the fish oil and not all fish oil capsules have them in it, especially the cheaper ones. Aim for 180mg EPA and 120 mg DHA per 10 lbs body weight daily. There is a large range of safety and it doesn't have to be that amount exactly but this gives you some guidelines.
There are various additional supplements on the market to help with brain health. The three most readily available are: Cholidin, Senilife and Novifit. As far as which supplement to try first, I do not think there is any general agreement on that. Between the cholidin, senilife, and novifit I would make my decisions on which to use based on cost, ease of administration and availability. I do not see a problem with using them all if cost is not an issue and you have a dog who doesn't mind taking oral supplements. There may be more benefit to starting with multiple approaches for a greater combined effect and backing off to a minimum effective combination if you get a favorable response. It is not always easy to track response as the symptoms can be variable and intermittent.
I would add the Anipryl if needed for better effect or as the cognitive dysfunction progresses. No treatment is immediate and so you need to give it a little time to evaluate the response.
I hope that helps. Please let me know if you have any further questions.