Am I overreacting?

Bit of a random one but feel I need a sanity check from fellow Irish people

In short, my (27f) dad passed away a little over a month ago. He was sick for many years (not a terminal illness but one that left him profoundly disabled and susceptible to infections) and after numerous instances of doctors telling us he was nearing the end over the past few years, it finally happened.

I've been very fortunate to be surrounded by plenty of loving and caring friends and family members who've messaged with words of support, offers of help etc etc. Something I've been struggling with, though, is piecing apart whether or not I'm reasonable in being a bit annoyed/upset at the lack of communication from someone I thought was a close friend.

She messaged me on the day of his death and of his funeral with some lovely words. I replied suggesting we have a call or meet up, but didn't hear back. A full month went by before she messaged to apologise for not contacting me, and cited work being busy as her excuse. This is a person who I thought I was really close to, who has slept on my couch when they've needed a place to crash and who I've collected from bus and train stations when they've been stuck.

I don't know whether it's grief that's clouding my reasoning, or anger that the rest of the world gets to go on living their lives, or whether it is actually quite shit of them to go a whole month without checking in, which is where I'm hoping you people of reddit can help. I don't want or expect people to be messaging me constantly, as I don't particularly want to rehash the pain of it all on a daily or weekly basis, but a simple message checking in would have sufficed.

Grateful for any and all opinions!

Edit to add that either way I don't plan to confront this person, I suppose really I'm just trying to figure out whether I'm being unreasonable / expecting too much

Edit #2: Just want to thank everyone for sharing their own experiences of loss and of supporting people with loss. I think based on the sage advice many of you have given me, the best thing to do is just let her know (nicely) how I'm feeling, as she's typically a really good friend and I wouldn't want to fall out over something that's likely explainable. Thanks a mill again!