(((((ACG and family)))))

I think Polly has really excellent advice.

I would add what I think you already know, that it may take your daughter several attempts to leave her boyfriend for good, so try not to get frustrated with her if she leaves and then goes back.

I think it's a good idea to let her know where you're coming from, but I don't think it's a good idea to put rigid conditions on your offers of help. Odds are that if she slips, she will feel too ashamed (or too financially strapped) to let you know. I know it's not what you meant, but it may feel to her like your love and support are conditional (which is what relationships tend to feel like to abuse victims, anyhow).

Take good care. Be proud of getting yourself out of that situation, and of being such a good mother.