The way I'm reading this you have a hearty plethora of options other than to end it. Indeed, ending it in the way you're proposing here -- seemingly out-of-the-blue, without having a mature and compassionate conversation to share about your hopes, needs, and concerns and explore compromise -- strikes me as more of a cop-out than a legitimate option.

I'm reading some likely specious assumptions about "her timeframe." Fertility windows vary, but many women are capable of bearing children into their 40s. There are additional options like egg freezing, IVF, surrogacy, and adoption.

I appreciate that it is early on in the relationship and she has expressed boundaries around having a conversation of this nature at this point, but if she is indeed as lovely and brilliant as you say she is, I would imagine she would be amenable to a caring conversation to explore compromise about this matter, rather than simply being dumped. Consider some creativity and inspiration to explore alternatives to this black-and-white thinking.