There are multiple ways and none of them involve BitVM. I'm not going to argue that you couldn't use BitVM, but right now that sounds like it would be overengineered.

So yes, you can create timelocks, you can even make multi-sig timelocks.

Alice could also sign a psbt that sends that Bitcoin to Harry and keep that in a safe or even give it to Harry directly, but the signed tx can not be mined until a timelock has been reached.

Liana wallet has a lot of this stuff: https://wizardsardine.com/liana/

There's also some inheritance related stuff you could do with CTV (or LNHance which is CTV + CSFS + IK [and yes even though Jeremy is being fucking stupid again withdrawing his BIP because he doesn't like that fucking ordinals didn't get a BIP, I still think his code at least is still good and I still would soft fork it if my peers would join me])