Girls, When should I message a girl I recently slept with?

Anonymous
Girls, When should I message a girl I recently slept with?
So for context:
I went out for a friend's birthday over the weekend, it was a daytime drinking thing which went on into the night. The woman (Let's call her Amy) I met is a friend of the birthday girl and through the day we all get drunk but me and her start to flirt. We all end up back at Amy's place. The birthday group decide to leave but Amy tells me to stay. I stay, we sleep together, wake up the next morning.

I have work to go to so leave quite abruptly, but message Amy later to apologise for leaving so suddenly and how I'd like to have stayed longer. I ask her out for a drink to which she says she's busy next weekend but possibly free weekend after.
This was on Sunday, Monday she added me on Instagram. We've not spoke since Sunday, should I message her, perhaps asking how her weeks going, or making a joke about something which happened on the birthday party?
I don't know her too well and our mutual friend has said she's quite a spontaneous person so maybe this is a regular thing for her.

Sorry if I've rambled here, I really quite like her and would like it to go well and I've been overthinking A LOT.
Girls, When should I message a girl I recently slept with?
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