Giving ownership to someone requires you to understand what you are doing and the legal impact. Besides the credit part that BQ mentioned -
She may be giving you some money now, but you are giving her equal ownership of the house. You break-up, she still owns part of the house. You want to sell, you need her written permission. You want to get a loan without her later - she still needs to sign the mortgage.
Check with a banker or lawyer.
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Integrity. With it, nothing else matters. Without it, nothing else matters.