Is this normal? Not talking about her mum EVER who died about 2 years ago? Should i ask about it more?

One of my best friends mom died but it was from cancer and she died 2 days before mothers day and it was a big deal and it took so long for her to say anything to anyone and her dad was never there and she lives with her sister and shes the sweetest girl ever; but what i would advise is if you bring up her mom don't bring it up like right away, but if she ignores the topic then just wait, it doesn't mean anything is wrong with her it just means that shes not over the fact that her mom is dead, my best friends died 2 years ago; both of them and I'm still in denial that there gone, its a normal thing its just the way people are; there hearts are keeping them in but there minds are saying let them go, but the heart is just as powerful as the mind so its a big thing, but just give her time and like i said if she ignores the topic then just wait until shes ready.