Whether you’re struggling or not, it depends.
If she uses your house like an hotel, i.e. gets/expects her choice of food, cleaning, laundry etc, then making a contribution is a useful lesson, besides helping with the expense of an extra person.
My DGD staying with us uses more electricity, (hairdryer etc) more water-frequent showers and laundry. (Minimalist packing means she does laundry every 2-3 days.)
She has a dietary issue which means she needs some different foods from what we like to eat.
She voluntarily keeps her room tidy and offers help with washing up etc.
As a guest, for a week or two that’s fine and in return, we get the pleasure of her company.
In the OP’s circumstances, I’d be asking for a contribution to household expenses. If her parents pay it, that’s their decision.
If the OP likes/is able to save it and give it her GD as a lump sum when she goes off on her travels, that might make her feel better.
That’s what we did with our daughters.