I was going to say both my kids gave up naps well before 18 months, but it was more like *I* gave up trying to force them to nap by then! They are definitely not daytime sleepers smile Usually I'd have to drive them around in the car, and even as babies they'd only have one or two 20-minute naps.
My rule of thumb is: if you're wondering if you should do something - do it! If your brain is trying to tell you something, it's usually for good reason.
If it were me, I'd just start waking her at 8am and putting her to bed at 8pm or whatever. It might take a few days of crankiness (so have some cool new toys ready) but it'd be worth it in the end. I couldn't bear kids being still up at 10pm! When would I watch my trashy TV?!