Whilst Marxism recognises the fact that women are oppressed (well spotted Marxism, I can see how we'd be lost without you, you bunch of pseudo-feminist wankers), it lays the fault for that at the feet of capitalism. So Marxist feminists subsume feminism into Marxism (or socialism, it's the same logic, and same outcome), and so hold that the only way to end the oppression of women is to overthrow the capitalist system, and end the oppression of everyone.
But by so subsuming feminism, they violate the absolutely fundamental tenet of radical feminism (or as we radical feminists would say, 'feminism') that the oppression of women is the most fundamental form of oppression. Marxists and socialists often call themselves 'radical', but they're a bunch of wankers, so ignore them.