@Inna22,
I am not social media savvy, but is there a way that I can follow on here or on another ABB board? You have some of the best thought provoking situations and questions.
Do you think the guest is trying to get you to lower you price, or she is genuinely in a different financial position, and is giving you as much notice as she possible can provide? Is the booking for the 5 bedroom that you're currently listing, or one of your listings that you recently put on snooze? If it's an inactive listing, your chances for re-booking are very slim, and it may be worthwhile to try to work out a price (or shorter stay, but same nightly rate) that is favorable for the both of your considering the circumstance. If it's the active listing, what is the likelihood that you would get a replacement booking within the next 8 days? If there's a good chance to get a reservation, then I suggest that you ask her to cancel as soon as, and you are willing to refund her money if the place gets booked.
Otherwise, I say stick with your cancellation policy, and do not bring up anything about extenuating circumstances unless she mentions it. In that case, I'd point out that guests receive vouchers, and they must be used on one booking. If the guest is truly in a financial tight spot, she isn't going to take a voucher that has to be used all at once on a less expensive space, and pay more, but potentially get less.