Who knows the number, but there are likely millions upon millions of marriages/relationships wherein at least one partner is a second fiddle.
Yes, quite so, and I am suggesting to the OP that she thinks carefully about whether she wants to join their ranks. She has a choice.
It's just not so in your face as this one could end up being.
Yes, but I am not suggesting that all such relationships should be immediately terminated.
It's not fair to a human to demand that one stops loving another just because that other is gone, for whatever reason. A person who demands total love, when that's not a possibility, is being unrealistic.
However a person who realises that the amount and nature of love that are in prospect are neither enough nor what she wants is not only entitled, but well advised to withdraw.
I didn't suggest that she make such a demand; rather that she thinks beyond that to consider what the totality of his actual behaviour informs her about his personality and situation (keeping her clothes, still displaying all her photos, contemplating a tattooed memorial on his body, unwillingness or inability to consider her feelings about these things)