Lagos has a reputation from times gone by, and yes it still has its danger areas BUT there are many friendly people in Lagos who are not out to rip you off and scam you. Half of the problem of 'dashing' is the educated westerners who automatically give in to a subtle demand for 'dash' instead of politely ignoring or refusing the request.
Just completed 3 months based in Ikeja and whilst you didn't feel free to roam the streets sightseeing, it wasn't impossible to find people who would show you around, and keep you out of areas that are the equal to the likes of Moss side in Manchester
I guess it is a bit different for a female on her own, but there were a few of us, blokes and girlies, that used to go off to the Chinese restaurant next to the Sheraton, and the one in Okeja called Chopsticks, and Londoners etc etc.
Providing you are sensible you won't have any problems over and above those found in any big City in the world