It won't work if she's got a halfway decent lawyer, but try and push as much property (at face value) on her as possible. She wants the house? Great! That comes out of her half of the settlement! At full value (which is hard to get on an open market). She wants the engagement ring! Great! Full retail value of the ring counts against whatever her settlement's monetary value is!
On the other hand, if you're smart enough to bail out of a relationship before you get married, but after you were dumb enough to pop the question, the ring is yours. An engagement ring could be considered the down payment on a contract to marry between you and your fiancee IF it isn't also a gift for something else. Some guys try to cut corners and buy an engagement ring as a combination engagement ring and birthday/Valentine's Day/Christmas/whatever gift. That's a bad idea, because then that's a gift to her, not a down payment on a contract, and she can keep the ring if you break off the engagement.
Yeah, yeah, it means an extra night out for popping the question and if everything goes through it means an extra present and dinner out every year that you can't wrap up into a combo day (ie- "Our anniversary is Valentine's Day, honey, so we only go out once that night!"). First, it'll never fly: you're going to be giving her two gifts for engagement day/whatever holiday anyway, and second if the engagement falls through you're out a good chunk of change if you bought a decent ring.