Tumor/bleeding I really worried

So a few days ago I noticed my little girl Vitani((my albino 1.5 years, unspayed female)) had developed what we know is a mammary tumor under her armpit. The vet looked at her and told me it should be benign and that i could get it removed soon but it might be best to wait a little longer in case it grows back again. However, at the vets, im almost 99% sure that she urinated blood, in front of the vet. Her cagemate was with her, so I am not positive that she did it, especially since she peed a little more later and it was clear. I have never seen bloody urine in their cage, and the only difference lately is the tumor and ive been giving them more fruits and veggies lately((not red ones that may be causing this)). I am a little upset because I went to the vet just for him to LOOK at her, since he wasnt charging me for that, but when the blood appeared, he told me it was not a reason to panic, that it could be stress. He is a certified small animal doctor. He told me to keep a close eye on her and if it gets worse that i would need to make an appointment. I feel like I need to be worried about this, and wondering if it is the tumor, or if it was just stress. They hate car rides, and they have never had good experiences at the vet. Opinions please <3

I'm not sure how he links stress to blood in urine; it could be a urinary tract infection, and myco infections can also affect the genitals. Is she on any kind of medicine right now? If it cleared up and isn't reoccuring, then perhaps it was a light irritation in the urinary tract that cleared itself up. You can try a bit of cranberry juice for urinary tract infections. Does she seem uncomfortable if you touch her in the abdominal or lower area at all? Is she over-fussing, licking, or focusing on the area? The tumor in the armpit shouldn't bear on the uterus or genital area, and if a tumor was also growing 'down there', I'd suspect the vet would have felt something amiss during his examination. If she's eating and drinking normally and the urine seems fine, then just keep an eye on things for a bit. Are you certain it wasn't something red in the bedding, such as some porphyrin that got wet, or any other coloring from fabric or otherwise? Usually a UTI is cleared up with a medicine like baytril or amoxicillin, but that would only be used if this reoccured. As for the mammary tumor, some people (myself included) have had luck shrinking them by using flax seed oil and cottage cheese blended well (2 parts cheese, one part oil) mixed with curcurmin, coriollus versicolor mushroom powder (sold at most health food stores), and goji berries. It is worth a try. Yes, they usually do grow back after surgical removal, especially if their bodies are programmed to grow tumors. But that's up to you. If you opt for surgery, make sure she has something to eat before surgery (rats don't vomit and need the energy from food) and that they keep her warm enough during, and when she's coming out of anesthetic.

Oh boy... blood in urine is cause for concern, specially since bladder infections can be quite painful too. I'd go back tot he vet and tell him there's more and get her treated asap.

No she isnt on meds, and its weird because they have urinated quite a few times today and none have been even slighty red. The blood that showed up was on a clean white rag that i let them sit on in their cage for car rides, and the blood was oddly bright. No toenails looked ripped, and no blood on fur around the vagina either. there was also no squeaking on the way, so i doubt they got hurt. She doesnt seem over fidgety. I wanted to try flax seed, especially now because this thing is growing fast. Im going back to a different vet on friday to get her opinion.

Blood in the urine is a huge concern ...

As for the tumor, better to have surgery when they are small as less invasive.
Also, getting rats spayed greatly reduces the chances of getting mammary tumours. The most benefit occurs if girls are spayed before 4 months but it is helpful at any age.
The most important thing is making sure your rat is healthy and that the vet you use has successful experience in spaying rats because surgery is not the same as with other animals.
See things to discuss before surgery http://www.ratshackforum.com/forum/showthread.php?t=7691