Congratulations on raising a healthy dog to 12.  Other folks have given really great advice.  I've seen a lot of dogs who seem to "run off a cliff" health-wise.  It's difficult to watch a dog so very healthy become old really fast.

Keeping the dog as active as she can be is important.  The right drugs can make all the difference.  I thought my Colt might retire at 8, then I met my wife and she put him on an anti-inflammatory and made me put some muscle on him.  Less pain = better work-out.  The extra strength and cardio conditioning helped quite a bit and he will hunt this fall at 10 (the age his father passed).  We've x-rayed his hips and await PennHIP scores, but we know they'll come back with minor dysplasia.  But he runs with pups still and is mentally sharper than two years ago too.

Chiropractic might be helpful in addition to or instead of drugs.  Colt gets adjusted every other week and our Rymadil supply is probably out of date by now.  Colt started jumping on the tailgate again, having took two years off.

I don't know the weight of your girl, but the less weight she has to carry on her achy frame the better.  The light side of ideal is ideal in my book.

Here's something most folks don't know...  A lot of veterinarians, maybe most of them, do not like working with geriatric patients.  Old dogs can't be "saved" from death, so a lot of them just don't like doing it.  Finding a veterinarian who likes geriatric dogs and is willing to work with you (and that means within your budget too) may be as important as anything else.  Hopefully your doctor does enjoy older dogs.

Diet, exercise, pain reduction and love...  It sounds like that's what you've been providing, and it's what she needs.

Our Maggie, who is liver/white english pointer, was our first adopted rescue dog, back in 1999.  Rescue did not know how old she was, maybe 2? 4?  She's had her share of injuries over the years, creating further arthritis for her. She has been on Rimadyl for many years now; 100 mg, 1/2 in AM, 1/2 a pill PM.  She is on glucosamine suppliments twice daily, and bladder control pills for several years. She has been loosing her hearing for a couple years now, so I try to keep it quiet at my house for her, cuz even tags jingling from another dog makes her grumpy, and I see her steer clear, so she is not plowed over.  She can barely get up anymore, and cannot jump up on anything but the couch, and I pay close attention, cuz sometimes she will miss.  I have to help her up the four back stairs cuz her back end is junk.  We discovered she had hip dysplacia a couple years ago when she blew her knee out.  We got lucky she had enough muscle tone to hold her hips in their sockets all these years, but she's got two big bumps on her back where her hip bones are now.  She pulls herself up now days.  Once she's up, she can teeter around, but is afraid of shadows on my wood floors, cuz she knows they are slippery, so I have rug runners all over so Maggie has more traction. If she makes it down my basement steps during the day, she cannot make it back up on her own, without that butt boost.  We did have her knee fixed, but it will never be the same. She cannot sit straight anymore.  To add to matters, she had two grand mall seizures in Dec or Jan, so now, to play it safe, she's on phenolbarbital twice daily.  She also gets skin absesses, which can appear outta nowhere fast. For instance my ex had her this past weekend, I sent her with him fine...she came back with a really swollen front paw, that has drainy absesses between her toes, so I keep antibiotics around for when that happens.  She has had allergies ever since we got her, so I keep benedryl around for those days.  We also had her anal glands removed a year ago, cuz those kept absessing.  So now, she will periodically fart out a hunk where she goes, or in her sleep.  URGH!  She has an eyelash on one eye, that curls into her eye!  I have to pay attention for that sucka, or she gets eye infections.  I just had to pull the thing out yesterday, cuz he returned her with a green gooey eye.  She has a big "wrist" on her right front paw from an old hunt injury, where she probably stuck her paw into a hole and pulled it out, distending that "wrist" and one of her toes causing her arthritis.  She is my episode child.  Every month it's one thing or another!  We decided if that other knee or her hips finally go, that's all she wrote for Maggiemum. So far, so good.  But it's very hard watching her in this final stage.  She now has what we think is geriatric bronchitis, always coughing.... And enlarged liver, making her belly appear very big.  I'm keeping her on Rimadyl anyhow, or she could never get up anymore.  I'm doing my best to enjoy whatever time we have left with Maggie now.   She still rules the roost at my house, and will still get up and fling a toy periodically.  She has been a money pit!  We just take it easy with Maggie now, while we watch and wait for her signal.  I know what you are going thru all too well.  Take care, keep us posted.         

I agree with Phyllis about natural remedies where possible.  I don't use Rimadyl unless I have to.  I tend to go with Deramax.  It seems to work better, my vet (who I trust) recommends it over Rimadyl.  I have a good friend who rescues horses and she has a very old horse who has all kinds of arthritis and inflamation problems.  She uses a juice that's packed full of antioxidents and it really helps the inflammation in her horse.  The juice is called Xango juice and was recommended by a vet in Central Texas who uses natural remedies where possible.  My friend swears it works and has extended the life of her horse who has been at deaths door twice.  Good luck and keep us posted.

Tears are in my eyes as I read your story of Heidi's last days.You provided her comfort care she most needed . My deepest sympathy for you and your family. RIP Heidi.