MrCuddles:
So far she’s gained 30 pounds since we’ve been together and she wants to hit 250 and go from there. She wants to gain till immobility as quick as possible is what she as told me. I’ve have been trying to keep her on a somewhat safe gain that way she doesn’t over do it and loses interest in it. But she’s more submissive in this relationship
Hm. I wouldn't do it if I were you.
To be clear, I'm not kink-shaming. I honestly do not care. But I don't think you two are ready for that.
Your profile says you are 22. I don't know anything about you, but the average 22-year-old is usually in college with little money. Gaining til immobility is a huge commitment. You need to be able to afford food, clothing, medical care, and mobility aids at high weights.
I don't know if you are the sole provider or if you guys are splitting expenses, but there will be a time when she will heavily rely on you for all her needs, such as feeding, toileting, bathing, etc. She might be able to get a fully remote job, but that's not a guarantee.
Feeding someone to immobility is akin to marriage in a way. Can you see yourself spending the rest of your life with this person? If not, then maybe you want to shoot for a lower weight. If so, then take your time and focus on getting yourself to a point where this arrangement won't burden either of you.