Tell her you love and want her to keep the baby, but that you will support her in whatever she chooses to do. Tell her you are aware of your problems and give her a strategy for you amending them, then tell her you understand that she needs space and give it to her, making it plain that you love her and would be glad to hear from her anytime.
Then let her go.
If she comes back it will be for all the right reasons and if she doesn't then sadly that's the way life is sometimes.