We had 2 beautiful dogs, one was a shihtzu, the other a Pekingese...
They were best friends, our oldest dog was Angel, she was 12, however the Pekingese Lily who is 3 was the alpha dog..

Our sweet Angel was so sweet and loving, but unfortunately she fell into our swimming pool after what appeared to be a brain aneurism... She went out for her morning potty and never came in, she was found floating in the pool, we found out that if a dog drowns then they will sink, she apparently died and fell into the pool according to vet... There were wet paw prints near the edge as it looks like Miss Lily tried saving her... My poor husband found her as we had searched the entire house for her, she had become deaf so we knew she would sometimes fall asleep in strange places and we always had to search for her, so that was normal...
He pulled her from the pool and this started a day of me trying to revive her and tying not to feel responsible for not being there for her..

It was a tragic death not only for my daughters and I but Miss Lilly is so depressed and has started peeing in the home...

Before we brought Angel to the crematorium we allowed Lily to smell her and see her, as I had read to do that so the remaining dog can move on sooner... the cremation services returned her to us with locks of hair and a paw print mold on a plaque, we allowed Miss Lily to sniff as we were directed by the vet..

But now I am at a loss of what to do for her, she is never left alone unless for a grocery trip etc.

Should I bring in a friend for her or what will help her?

She has been hiding her treats (she never did that before) and she has been house trained for over 2 1/2 yrs, but now I find puddles everywhere..

Any insight or advice will be most appreciated.

Dogs mourn like people do. Since they can't sit in a room and have a good cry, they resort to other things.

When she does pee inside what is your reaction? No matter how she's feeling she needs to know that peeing indoors is not okay, and not acceptable behavior. You'll have to treat her like a new puppy you're potty training, back to basics. A firm no when you catch her in the act, then take her directly outside. Stop her mid pee if you can. Once outside, use your potty word, and tons of praise when she does what she's expected to do.

How often is she walked? How often does she get a chance to potty?

As for getting another dog, I'm a firm believer in finding a new friend for a dog that's lost theirs, but it can be a lot of work. There's no guarantee that the grieving dog will accept a new addition, so I highly recommend that you take her along when you're making your choice. I'd also recommend a rescue dog around her age, and energy level. It's trying at the best of times to have a puppy in the house, but for a dog that's mourning it can make things start of badly for the two of them.

First get her potty issues under control. You really don't want her teaching a new dog bad habits.

Good luck, and I'm sorry for your loss.

Reduce the areas of the house she can reach for a while. She hopefully will be less likely to pee in a small area. Close doors and put up barriers.

Just spend a lot of time with her while she mourns.

I'm so sorry for your loss. We knew we'd lose our beagle and tried to locate a rescue after we lost him. Our remaining dog had never been alone and wouldn't come out of his dog house. We got a puppy within two weeks and our dog seemed to understand it was for him. It took a bit of time, but once she could play a little tug of war, they bonded. We're at the 6 month mark and they are best buddies. Good luck with whatever you decide to do.

A friend of mine recently lost her cat in a sudden accident, the cat and her dog were best friends, they were inseparable. The dog pined and moped and continuously looked for the cat, in the end she bought a new kitten home and they bonded instantly.

Unfortunately that is not always the case, but in her circumstance it worked perfectly.

Another option may be to buy one of those toys for kids that simulate a real dog. There are a lot of different ones, the ones I think would work best are the ones that just have a bit of movement, I bought one for my mother last Christmas and you would swear it is real, it's in a curled up sleeping position and when you turn it on its sides rise like it's breathing.