If you want to practice polyamory, and you want Anne, tell her you've recently opened your marriage, and you're poly. Isn't part of "love" getting to know each other? If you're afraid to scare women off just by being true to yourself and telling the truth, maybe it's time to retreat and see why you are coming across as ashamed of who you are.
OTOH, if you're proud of who you are, and can own it, you'll find the right new partner. If Anne is "scared off" by polyamory, or the way you practice it, well, she's not the right "gal" for you.
Seems pretty straightforward to me. Personally, I date from ok cupid, and my profile states I am ethically non-monogamous, and that I have a live-in gf and a nearby married bf, and am still open to someone who is cool with that.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
me: Mags, 59, living with:
miss pixi, 37