Hi

Okay, there's a lot here. I will try to give you answers to the best of my ability and knowledge, but admittedly, I think I was 5'2" once, in like my freshman year of high school. Same with the 140 pounds, let alone the 125. I was 135 and my current 5'5" not 9 years ago, but wasn't doing keto then.

My answers will be gleaned from various sources, though I only just received my Keto Clarity book and have not read Fat Fast (though I just completed a fat fast with a 4 pound loss as of last Sunday).

So, disclosure aside... here's what I've got:

Hello there, I'm a 5'2 woman , 140lbs with the goal weight of 125lbs. Ive been on keto for 6 weeks and out of the "keto flu" for a month and no adaptation yet . my keto meter has been reading 0.7 for 3 weeks but im still drowsy , generally unmotivated. Im not sure of what I am doing wrong !? ..so Im resorting to a fat fast and Im on day 2 out of 5 hoping to break this wall im facing .

Are you trying to get to the "optimal ketosis" for fat burning range of 1.0 - 3.0 mmol/l?
There are some that think that better fat burning for them occurs between 0.5 and 1.0 mmol/l. You don't have much to lose, so it might very well be painstakingly slow.

Is there a time period between the keto flue and adapting ? or does it go straight from the flue to the golden state?

I've never seen anything that can give a definitive to this, but from various sources, this could take weeks to months to become adapted.
As with most things, everyone is different.

Does weight come of way slower if you don't have that much to loose?

Yes, much slower. Slower and slower as one is nearer to goal weight. Again, in most cases.

And is there such thing as eating too little calories to adapt ?

There is eating too few calories to get meaningful macros. Obviously, 85% fat isn't going to be as meaningful at 800 calories as it is for 1000 or 1500 calories. The ubiquitous "starvation mode" is more like 'slow down' mode. Losses slow. One will eventually lose, but the body is protective of dying. If you're eating too few calories to meet your BMR and activity needs, you may be slowing yourself down, including optimal ketosis.

Ive read some people water fast to get into ketosis but can one fast to get adapted?

If you've been subsisting on 800 calories for a while, I think I might try more calories, like at least your BMR to see if you can get your metabolism back up to where it needs to be. Calories play a role in losing well, but it can have diminishing returns if you go too low. You can always reduce later once you know what your body is doing with keto on your full allowance of calories.
15 grams of protein is very low (as the previous poster stated).
At Phinney and Volek's low range of 0.8 gm per kg lean body mass (63.64 kg), I get you should have a minimum of 51 gm protein a day, more if you're active. Your body will catabolize it's own muscle to supply energy/nutrients (potassium and sodium) if you aren't supplying them in your diet.

Now my questions:
Are your fats most saturated fats? Coconut oil? MCT?
Are you taking any supplements while being on such low calories? If so, which ones?
Just what does a typical day of food look like for you?
Are you measuring your body to be sure that you aren't getting losses there when the scale isn't showing them?

When I started this in March, I had a heck of a time with my abdomen and getting more than 650 calories into myself. I kept inching up the calories each week and challenging myself to get to some type of normalcy. I found that I really couldn't get all my protein and other nutrients in with so few calories, so it was critical. As I increased the calories, it became much easier to balance things out, and my losses have stayed about 2.5 pounds average a week - but I have MUCH more to lose than you do! I will probably continue to lose at a much faster rate than you simply because I have more to lose than you do. So don't be keen on comparing yourself to others too much. You're a unique snowflake and you will lose in your own time.

I am not sure how you feel about unsolicited advice, but I would go to 1300-1500 calories (as you are doing) but also adjust the macros: 70% fat, 20% protein and 5% net carbs. Include a salad once a day, 2 cups of chicken broth, and some more protein (pork, chicken, almond butter, salmon ect)

Your body probably thinks it's starving and it holding on to any excess fat like it is going to save your life. You will probably feel bloated after the first week with vegetables and fiber added, but the water weight and any constipation issues would probably clear up.

I know it is a month from when you posted, so I don't know what you are doing now. I have problems with anxiety too and in my experience it can lend itself to obsessive behavior.

Hope you find what works for you.