What a horrid situation to be in. If I was you I would ignore a whole night's messages and in the morning I would reply to her saying, "Sorry, turn phone off after work now, talk at work".
When you get to work, she'll ask why, tell her it's a new house rule, so you all get to enjoy family time together without constant distractions from Facebook, WhatsApp,Twitter, messages etc
If she asks emergency emergency, tell her then family will call house phone (which is family only).
Going forward, continue ignoring messages (mute them) but dont reply in morning, just tell her at work that "yeah, my phones off in the evenings, i did tell you".. she'll stop messaging at some point.
As for the talking in front of managers about job searches, tell you are happy here & she should go for it.
When she needs help, tell her to ask her manager as your busy and wasnt paying attention to what he asked of her .... maybe she'll then pay attention and stop asking you to explain everything.
I think you can do this without being rude, just appear busy whenever she starts bothering you, she needs to learn to stop being so needy.
It's not your job to be her carer, you just work along side her.