I married Aela so she could be a follower and help me with quests... TBH though I like her original outfit from the companions and I dont really want to put armor on her. Can she die from me and/or a Draugr or a bear or something?

Yes she can die, there have been many posts here from wife murderers complaining that noone else would marry them.

If you hit her hard enough.

She can only die AFTER you marry her. Before that, she's an invincible powerhouse, because she's essential.

So, your spouse can die. But fret not, Ancient Nord Armor (Aela's default armor) isn't exactly 'crappy'. But her Light Armor skill is significantly higher than her Heavy Armor skill, and Ancient Nord Armor is Heavy.

Companions can die after they have been "downed".
The companion will go to his/her knees and admit defeat. While in this state, attackers will not target them, but a stray arrow, area of affect spell will do them in for good. Also, while they are down, you can kill them if you hit them on accident or on purpose.