Miss Ina

Bingo! Definitely a bitch. She wants to make herself feel better by telling herself she's not "dumping" you (and won't hear of anyone else telling her she did, not even you), she's "letting you go", which makes it sound like she's doing it for you, not for her own selfishness, which she IS. She also prepared for making herself feel better about dumping you by doing the open relationship thing, so it looks to an outside observer that she was just breaking off something loose, not an actual "relationship".

Some people have real open relationships. I could never do it personally, but I know people who go for that. But that, my friend, was just something she made up, gave the title of something that exists but not in that form, and used it to make herself feel better for being a total bitch!

I hope you feel better soon. Getting dumped feels terrible, I know, but things will turn around soon.

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The word "time" split its husk; poured its riches over him; and from his lips fell like shells, like shavings from a plane, without his making them, hard, white, imperishable words, and flew to attach themselves to their places in an ode to Time; an immortal ode to Time.
—Virginia Woolf, Mrs Dalloway