I'm sure it is not unheard of for an 8 month old to go to 1 long nap, but I think it is more common for it to be a little later. My kids didn't give up their morning naps until they were closer to 15-18 months. She could be teething and it is just interrupting her napping. Also she is learning all sorts of new stuff (talking, standing, crawling, walking) which would make her not want to sleep even if she needs it.
Is she taking her naps at the same time of day everyday? My kids (3,3,2,9months) took their morning naps around 10/10:30 and I woke them up by noon at the latest. Then they still take their afternoon naps around 2 pm and sleep until 4/4:30. Depending on what time her second nap is, she might just be "catching up" from her 1st nap?????
Regardless, kids go through many phases and she might not be sleepy this week and next week be exhausted all the time! If you keep the times roughly the same, it will be easier to know if she is suddenly no longer needing a nap or if she is just not WANTING a nap...
Don't know if I answered your question or not. Hope this helped somewhat!