baby name fight

Apryl • 🇨🇻🇵🇷👭🦄🍀
So i was stuck set on and in love with the name Oliva "Grace" if its a girl but when i told my sister in law she told me i caint name the baby "grace" because thats the name she chose if she has a girl which shes trying for because its her husbands grandmothers name, but i feel like what if shes doesnt have a girl now i plan to do a reveal party so im not sure what the sex is but i really liked the middle name and now im looking for a diffrent middle name and having trouble im alittle upset bevause im almost 5 months and shes not even pregnant i loved the name and was set on i want to just tell her im keeping the name be ause its my choice should i? am i wrong? am i overreacting?