Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Now Dr. Peter is correct in regards ***** ***** lass's signs. Increased frequency and straining while producing urine and blood/clots in urine are not signs we see with constipation. (They cannot strain to pass feces hard enough to cause this). They are instead signs that we see with bladder based conditions like bladder infections, urinary crystals, bladder stones and bladder tumors. Therefore, I would note that these signs are just as important as any constipation and you will want to look into this (ie have a urine sample tested +/- examination by her vet) for her. Because infection will require antibiotics and the others may need treatment if present.
That aside, we also have to appreciate that there is no rule to say that only one thing can be amiss at a time for our kitties. Therefore, if you have not seen her pass stool in the past 48 hours, then she may also be constipated on top of having an uncomfortable bladder condition. They wont' be directly related but both are common troubles for older cats. And in that case, I would outline some steps you can take to try to aid her passing feces until she can be seen by her vet for her bladder.
First, you can help relieve mild constipation at home with some cow milk. Kitties are like little lactose intolerant people, and while the love milk it can move things down the gut a bit quicker (ie. Cause mild diarrhea in an unconstipated cat). If she is mildly constipated, this might just get things moving in the right direction.
As well, you can also treat her with cat hairball medication (ie. Catalax). This is available from the vet or the pet shop. It works to lubricate the gut and can facilitate the movement of hard feces out of the rectum. Alternatively, you can administer a small volume of a GI lubricant like Miralax (1 tsp per 24 hours), lactulose, or mineral oil orally. Ideally offer this in food, as this is the safest way to administer. If you do need to give it via oral syringe then take care to avoid aspiration (since that would cause problems we'd best avoid).
As well, if she is eating you can mix in some canned pumpkin or a 1/4 teaspoon of unflavored Metamucil. Just like people, these can restore fecal output regularity. I would offer these with wet food to ease her eating of it, while making sure we are getting water into her (as canned food is 35% water). As well, you also want to encourage your cat to drink as constipation can be complicated by dehydration. Make sure she have fresh water and you can even offer low sodium chicken broth if she won’t drink. That will help any fecal issues and also help flush the bladder and give her some relief.
Overall, if you have seen these signs and she isn't producing feces either; then it sounds like more then one issue is causing her grief. Therefore, you can use the above to help her pass stool but if she has blood in her urine, then we'd need to consider a check with her vet to diagnose a possible bladder infection, rule out those other worries, and get her onto treatment to soothe this for her.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,