Can the calories be increased to 1,800 which is more realistic

You can set your calorie goal to whatever you want.

You got 1200 based on what you inputted to MFP

Go here:

https://www.myfitnesspal.com/account/change_goals_guided

And update "What is your goal?" to lose less per week.

I started off with 1200 too, and I realized by lunchtime the first day that wasn't going to work for me

Good advice above, and I endorse considering picking a slower rate of loss, or adding some exercise if you can (even quite gentle exercise if that's what's manageable - it's a myth that exercise has to be intense to be useful).

I'd also add that it may be worth a look at *what* you're eating - most people find some foods more filling than others. What is filling is very individual, but here are some common things (not univeral things!) to consider:

Some people find filling things to be:
* Protein foods. It's fairly common among us mature folks (I'm 64), especially women, to get lower than ideal protein. Getting more *might* be more filling, and contribute to health, if you're on the low side.

* Fats. Many people cut fats way, way down because they're calorie dense. But we need some. For some people, they're especially filling, besides. (It can be useful to favor sources like nuts, nut butter, seeds, avocados, olive oil, fatty cold-water fish, etc.), so not exclusively fats from red meats and full-fat dairy, though some should be fine.

* Whole foods. I'm not doctrinaire about this, and think processed foods, even highly processed foods, can have a place in nutritious eating. But it's unquestionable that many people here on MFP report finding that for them, personally, including more veggies, fruits, whole grains, and that sort of thing in their eating helps them to feel more full on their reduced calories. If your eating now tends to be high in processed foods, it might be worth shifting that balance a bit, if you can think of whole foods you enjoy.

* Volume. Some people find "big" foods filling. This can be high-fiber but not high-calorie things like veggies, foods (not just drinks) with high fluid content (like soups, stews, juicy veg/fruit like tomatoes or watermelon, etc.), whipped-up things (people sometimes make a fluffed-up pudding-style things from protein powder, for example), and more. There's a whole thread in the food part of the forum, where volume eaters share ideas.

Another thing that can help with feeling full/satisfied is trying different eating schedules. I wouldn't urge doing something truly extreme at a mature age, but people here do anything from all-day grazing to very structure 3-meals-plus-snacks, to one meal a day, and everything in between. Some people do better skipping breakfast and going for a brunch/dinner setup with bigger meals, others (I'm one) can't get through the day without a solid breakfast soon after waking. It's all very individual, and can take some experimenting.

So, yes, increasing calories above 1200 sounds like a good idea, if you're struggling at 1200. Slower but reliable loss gets us further than theoretically speedy but in reality unsustainable loss. I was able to lose pretty well, at quite a bit over 1200, even at age 59-60 when I lost 50+ pounds. For various reasons, I don't think my exact calorie levels would generalize to others, but more than 1200 ought to be workable for most women, even more mature women, at a slower but sustainable loss rate.

Best wishes!