Is it okay if I tell my friend that it was weird of her to make such a big deal about her fish dying?
That's horrible! Why would you be so heartless?
Mary should get over it, and she'll be proud of herself when she does
It's good that you are willing to be honest with a friend, but you will upset her if you say what you are thinking. Your friend has lost a pet that meant a lot to her, and you should let her recover on her own schedule.
My friend is taking the way too long to get over the death of the fish and i'm sick of hearing about it
Let her grieve at her own pace, you can't understand how much a pet means to you since you weren't the one to raise it and take care of it. Give her some space and let her know you are there if she needs any support.