My gf [30F] and I [26M] recently went through an extremely difficult time a few months ago. Jan 2019, her 7 year old son passed away (epilepsy). She also has her daughter (10) and I have my son (5). 

We have been dating for nearly 2 years now, and have an extremely healthy relationship. Amazing communication, trust, and intimacy. We plan on moving in together the summer of 2019, just a few months away. Considering it's me, her, and our 2 kids, I plan on getting us a 3 bedroom house. Here is where the issue comes in:

She suggests that we get a 4 bedroom or 5 bedroom (4th bedroom would need to be for my office, as I work from home). She wants the extra bedroom to put together her son's room exactly the way it is at her house now (she hasn't touched it since the day he passed, understandably so.) I informed her that buying a larger house is going to really be stretching our budget, and we may not be able to make it happen.

Please note that at this point, I have not exactly expressed to her that I don't want to use up a room on a replica of her son's room. It's space that we would actually need to use (God I feel terrible even saying that.)

At one point, she even suggested that if we get a 3 bedroom house, that she would put her son's stuff (bed, dresser, clothes, etc.) in MY son's room. I just don't think that's fair to my son to have to go through that.

I love her very much, and plan on proposing later this year. Our kids love each other and we are an extremely happy [blended] family. Obviously there's no way she can be the asshole in this situation, considering she's just grieving from the tragic loss of her son, but I honestly feel like I'm not being exactly an asshole either..

With that being said.. Am I The Asshole for not wanting to use up, or spend extra money on a significantly bigger house, for her son's furniture?