Kmssith, i totally understand why you wanted this holiday but it wasnt your intention to pay for denise. If it had just been your share you would have had money to take care of heating and very important doctors appointments.
At this point i would condider a family member or someone you knoe who id fun but condiderate and would be prapared to pay for at least part of the expenses laid out. I wouldnt be suprised if denise expects you to pau her food, drink, taxis as well. Please keep us updated and i would remind denise that you are unwell and point out the sacrafises you have made. They do say in difficult situations you find out who your true friends are. I think you have found out that denise is not. I think you need to be blunt with her and let her know she is not being a good friend.
I wish you a wonderful holiday