So you are proposing the following -
1) You lend daughter €200k
2) She buys new house with cash
3) She sells existing house in time
4) She pays off mortgage with proceeds of sale
5) She remortgages new house to repay you
There are almost no tax implications of this. Your daughter would be assessed for gift tax (Capital Acquisitions Tax) on the interest on the loan. As it's well within the mother/daughter threshold, no tax would be payable. I don't think you would even be expected to report such a short-term loan.
However, I see a problem with Step 5 - lenders are not doing remortgages at the moment. She will be applying after she has bought the house, and the lender will probably say no.