Skip a feed and dont give her any treats, then give her small feeds of boiled chicken. If you feel you need the aid of a supplement then Slippery Elm Bark Powder from the health food shop is great, just sprinkle a little in her food.
Once things have settled down, I think the best thing would be a raw diet but if thats not suitable then a wet food diet or homecooked (wetfood/cooked - you need to slowly wean from the chicken to that food over a few dys to a week, this will avoid tummy upset). At fourteen the dry foods, if they are not already used to them can be hard work on the kidneys as it can dehydrate them a little, then they tend to drink a lot at once and bladder control isnt as strong as it used to be at 14..
A raw diet makes cleaning up the poo a LOT easier, but a diet that suits you to feed is also important. As long as you find something she does well on then her poops will improve and be easier to lift. For now you probably need a spade and some disinfectant, once her tummy settles, poo bags or nappy sacks are easiest, just check the yard daily and lift as needed.
You can train them to go in one spot but at 14, well if it was me, I wouldnt bother too much now, once her tum is better have a regular feeding schedule and she will 'need' at the same time each day so you take her for a little stroll then, not forgeting your poop bags and that way she isnt 'going' in the yard.
ADD; please dont panic, if she is ok in herself she should be fine but if the diahrea worsens or persists even after the 'starvation' and bland diet of boiled chicken breast (you can add a little boiled white rice too if you wish) then its time to take her for a check at the vets.
Here are links on homecooking and raw diets for your dog, somewhere you can start your research to see what you think she would do best on, personally at this age a raw meaty lamb bone once a week and a sliver of liver and on the other days 2/3 cooked lean meat such as chicken or turkey, 1/3 plain white boiled rice, rotate the meat source each week for variety and she should do fine thats if you choose to cook instead of raw.
http://www.bornfreeusa.org/facts.php?p=359&more=1
http://www.rawlearning.com/rawfaq.html
http://rawfed.com/myths/index.html
http://www.drbasko.com/nutrition.htm#dog_diets
http://cookforyourdog.com/index.php?option=com_content&task=view&id=30&Itemid=39
http://www.foundersvet.com/home_cooking.htm
http://www.foundersvet.com/raw_diet.htm
http://www.barkleyandpaws.com/Dogs/Nutrition/Home_cooked_dog_food___Give_your_dog_a_balanced_diet_200806171374/
Phew, I think thats plenty info for you but any questions just add details.