a little bit is the answer, they wont take any of her money towards your debts so dont worry about that.
Where they come into it is as follows, they will usually ask about all the household income and outgoings regardless of how you normally split it yourselves. The reason they do this is that she will be expected to pay a proportionate amount of the household bills, so for instance if she earns 50% of the income she will be expected to pay 50% of the household bills and so on. thats as much as she is involved