What is interesting about this is that I've pretty much described Elly. Granted, she was never able to cut and run from something that scared her as easily as Ted could and thus is more inclined to regret choices she wasn't able to back away from than he is but she does tend to mutter "if only" herself. She also shares Ted's tendency to use the past as an excuse for a failure to act. Just as she stands around bellowing about walking dolls, earlier curfews and busy babies as an excuse for not having the courage to do anything other than whine about her problems, Ted has the irritating habit of alluding to how his pooor mother needs him and how he's honouring the memory of a reckless idiot who he should have outgrown when he tries to explain that change scares him.
What this all means is that Ted is not only a bad person because he stands up to her. Ted is also a reminder of her own lack of real courage and her fear of actual growth; as long as he exists as an active presence in her life, she has to face the fact that she's a lazy, passive idiot who likes to complain....and that would be just awful.