Relationship advice. New relationship and Marriage?

So im in a relationship with my brothers wife s sister for 4 months now and its gone by so fast.

We have actually known each other for 10+ years but both of us have been single for about 3 years now and thought its time we get together and start a family etc we are not getting any younger.

She wants to get married before she completely commits or at least be engaged.

I just want to know if you guys think this is moving way to fast.

I am emotionally attached she is back overseas atm and we are trying to do a long distance relationship after living together for 4 months.

but i think my feelings are stronger... it kinda hurts.

I am wrong to pursue this?

its so fast i cant tell if anything is real or not.