Sick Guinea pig symptoms? Help!

I am very new to this forum, but I thought I'd join to see if I could get some help. My one piggy, Posey, has been peeing blood, not eating, and has not been drinking either. When I went down to see them this morning, there was a large blood stain and I became very alarmed. There has been no bloody urine since then. She also seems lethargic and has not tried to make it up the ramp in the cage to her favorite spot, while her cage mate is still able to. I am very very worried about her, because she is only 4.5 years old. She has exhibited some signs of aging such as decreased activity and slightly curled toes. I have not seen her squeal when she pees. I am 16 yrs old, so my parents will not let me go to the vet with her no matter how much I request :'( I have been searching up natural remedies for the past 5 hours and have been checking on her consistently. I suppose that blood in the urine means that she could have a UTI or stones? My mom went out to get cranberries as I heard that they help with UTI symptoms. When I tried to feed her cranberries, she refused while her sister has a little nibble and then became uninterested. Nonetheless, my piggies are very picky and refuse to eat any other veggies other than carrots. I always have a fresh supply of hay and good quality pellets, but it seems as if those have been left untouched too. Anyone have advice? I don't know what I possibly could do since my parents refuse to take me to the vet with her because of the $300+ expense. I hate to have all of this happen on xmas eve :'( I am just trying to keep her in a dark, quiet environment for now and just consistently check on her. I sincerely hope she will be ok.