Cat had urinary crystals but is still miserable, vets not sure what is wrong

Hi everyone! I could really use some outside perspective as I'm kind of lost. My 13 year old cat Julie is acting lethargic, barely affectionate, and sits around looking sick (meatloaf position, downcast eyes). Sometimes she is sort of herself, acts affectionate and then starts looking miserable again.This started in August along with frantic straining to pee and blood in the urine and was diagnosed with stryuvite crystals in a urinalysis. She's had this before, but this time cranberry juice didn't help her like it did in the past, and only once we switched her to C/D food did the straining to pee and blood in the urine stop.

We got her a follow up urinalysis and the crystals are gone. She's getting out normal amounts of pee, and isn't frantic about peeing anymore (though she sometimes rises to standing while peeing?) but is acting miserable.

I thought she had might have cystitis, but the vet said she definitely doesn't because there is no blood in her urine (is that definitely true?). She said we should wait it out, give it time, maybe she is just adjusting to such a big lifestyle change (she was on free feeding dry food, now on canned food), maybe it's an emotional issue because our other cat died a month ago and she is now left with her sister who hates her.

It's been a month now and she is still acting like this. The vet said next step would be ultrasound but she said she still wants to wait to see if it just gets better on its own because she doesn't really have any symptoms aside from lethargy and a little weight loss.

I consulted with an internal medicine specialist who agreed, saying that without vomiting, inappetence or blood in her urine they don't feel that confident they'd find anything wrong. But here I am sitting with my cat who is acting sick, and am struggling to accept that nothing is wrong here. She seems like she is in pain and no one really knows why. Am I being over cautious? She's had two perfect rounds of bloodwork over the last three months. I'm not even sure what direction to go in, and the vets seem very unconcerned.

She also has a subtle unexplained head tick, facial twitching thing that she has had for about a year that internal medicine vets in NYC vets also don't seem worried about. In the past she had two episodes where she threw up, started screaming and passed out. After ruling out more dangerous things, the vets ruled it was an allergy to a food change/asthma. That's why I only just changed her to C/D a month and a half ago. Maybe I'm just not giving it enough time for her to adjust? I don't know. Any thoughts on this situation would just help so much. Thanks for reading.

My partner in rescue has told me that the slight head tremor is neurological. Her old dog started doing that before he stroked. Not to alarm you but like you I believe your vets have been a little too casual about all this

Her kidneys and T4 were normal? What is her urine pH? Any chance she has some arthritis going on is she walking slow or moving slow? 

It could also be depression from the loss of your other cat.  Cats are very sensitive to things like that, and sometimes it takes them a very long time to get over losses, especially if she was good buddies with the one who died, and enemies with the one who is left.  Are they fighting a lot?  She may be withdrawing to avoid having to defend herself. 

We have another member who had to put one of her cats on an anti-depressant after another of her cats died

Yes, it sounds like depression to me, too. Try holding her and giving her lots of attention. Let her know she's loved and that you understand her pain. It will help her adjust.

The head tick doesn't sound good to me, and it's probably unrelated to the loss of the first cat. I would insist on that being investigated.