[puckhog]

I think the biggest thing to keep in mind is that it will no longer be your space alone, but yours jointly, which is a deceptively big adjustment. You might spend all of your time at each other's places right now, but figuring out how to merge your separate spaces is a challenge.

It sounds like the plan is for her to move into your place. Without knowing your situation with respect to leases, ownership, etc., I'd suggest considering looking for a new place together, if possible. From my own experience and watching friends go through the process of moving in with their SOs, the simple fact that it is "your" space can be a huge source of friction. If she's looking for a place to put some stuff for her hobby, you might feel like you're giving up your previous set-up and, on the flip side, she might feel like she's being shoe-horned into your space. Just by fluke, when my wife and I decided to move in together, we had to look for a new place, so we were both getting established there together, which reduced (but didn't eliminate) those issues.

If that's not possible, try to keep it in mind during the process. Make compromises in fitting in things she brings (furniture, etc.) and consider looking for things you can buy jointly (maybe your bed or couch is due for replacement). But, also stand your ground where something is actually important to you.