Well firstly, it's her house and she's doing you a favour, so if she doesn't want you to have sex then don't do it.
We lived with my OHs parents for about 3 months when we first moved here and it was really awkward (we lived in their living room because there wasn't enough bedrooms). We realised they were helping us and putting themselves out hugely, so you have to have a lot of consideration for them.
I hope it all works out well for you

It doesn't have to be a disaster.
xxx