Firstborn is Heartbroken

We have a 3 1/2 yr old daughter who has been excited about being a big sister since the second we told her....however she was convinced we got to pick out the gender of the baby despite how many times we tried to explain it doesn’t work that way. She had her heart set on having a little sister...we found out today we are having a boy (my husband and I are excited either way and a healthy baby is what’s most important to us). My daughter asked me later today if we could get the baby to change his mind...and when I asked if she would still love a little brother she started crying and said she didn’t know. It broke my heart. I’m sure she will come around and it is probably best to let her come to terms with it in her own way—but I was wondering if any other mommas had gone through this and had any advice?