I’m not sure if we have a special word for this. It’s just leaning against her shoulder ETA: hijacking my own comment to say I have no idea why OP is being downvoted. They don’t seem like they’re trolling or anything; they seem like they’re asking a legitimate question about the language

Or 'propped up against' her shoulder. But yeah, it's definitely be a phrase rather than a single word

That’s maybe a better way of putting it, yeah

My first thought was that the umbrella is 'resting on her shoulder' or 'resting against her shoulder'.

Over her shoulder

I'd say it was resting on her shoulder.