Obligatory on mobile so sorry for formatting

Me (f27) and my partner (m28) let our our friend (f26) sublet a room in our apartment after she had some financial hardships 1.5 years ago. It made the most sense at the time, we had a 3bed/3bath apartment and only used the rooms for guests if needed and it would be a cheaper rent all the way around.

Now we just bought our first house, and she asked if she could move in with us in our house. I originally didn't want that, since we're starting our life together and planning a family, and most importantly can afford the mortgage on our own. But we talked and agreed that it would be fine, and gave her a very accommodating rent for the in-law suite. Suite is 1bed/1bath private entrance with shared laundry with us, we also have a pool and fire pit she would have unlimited access to.

Now we have furniture from our apartment that we previously decided would go into the in-law suite, before even agreeing to have her live with us, and went I went over the lease with her she didn't bring up any issues. She then went to my partner and told him "OP will be upset but I have a couch I want to bring and move in, so she can get rid of hers I don't want it".

I'm irritated since we had already talked about the place being furnished, and we're giving her a significantly cheaper rent then she would ever find in our city. And the fact that she didn't talk to me about it, but went to my partner to try and get him to change my mind (I'm not sure if that was her intention but it did cross a boundary for me)

WiBTA if I had a conversation with her about how this isn't the same living arrangement we have the apartment, it's not her house and we can furnish it how we want, her only decision is whether she wants to live with us at that rent price? I'm trying to be reasonable, but on the other hand we have been overly accommodating (lowering rent $300 so she could afford it and stay in our city instead of moving).