Precisely she suddenly throw you this bombshell question unaware; What will surely be your reply to this as a matured dude

My plans are in the hands of the Almighty who made heaven and earth.

4years? Ladies should start getting senses naa, haba

We are all pencils in the hands of the creator

The main question is: what exactly do you want from the relationship with her?
Whatever is the answer to that question, is exactly what you should tell her.

Any other answer...then you're living in denial, and also deceiving her.

It's that simple!

Why would anyone date someone for more than a Year if she's expecting marriage?? 6 months is enough if you want marriage. If within 6 months all the hints you've been dropping are going unseen then it's time to find another husband to be.