She always gets her period regularly but it has lasted this time for 3 months straight .
Sometimes its blood and sometimes its not .

Umm... I don't know I'm only 11 but I would say no. I think it's only like a week. At this moment in time I haven't even started.

Ok, if this was you ( a adult) would that be normal,? Of course not, why after a few weeks did you not have her into a doctor ?

Please take her to the doctor and ob/gyn. It's not normal. Periods can be irregular in teens, but are not usually continual.

She may have developed a cyst on one of her ovaries. My sister had terrible periods until she was operated on and the cyst removed when she was 16. Please take her to a doctor for an examination. This has gone on way too long to be normal. If anything, this condition can seriously make her anemic losing too much blood over a long period.