Take a breath!
There are bad LPNs and bad RNs. She sounds like a seasoned LPN who has a great capacity to mentor a new RN and chooses to prove her superiority by pointing out your flaws and mistakes.
Perhaps you could try and have an adult conversation with her? Tell her you appreciate her knowledge but feel constructive criticism would be more effective than simply being critical.
She can't "get" you fired if you are doing your job. Make it a policy not to make the same mistake twice. Be teachable. If your ADON wants the census documented a certain way, then do it that way. If she asks that you be more specific with your time documentation, then do it that way. Don't be concerned about what everyone else is doing. I don't document "9:12p" but I will document "9:15p". I round to the quarter hour. It's not a big deal to check your watch.
There could be an element of "hazing" going on. They might be trying to see what you are made of. Once you prove your chops, they will probably lay off.
Good luck and keep your chin up! Oh and keep in mind, your pregnancy may be exacerbating your feelings as well. I always took things WAY more personally when I was pregnant!!