Someone please help me figure out my LO's sleep issue before I lose my mind. I'm not sure if this is regression, teething, stress, nightmares or what...but I can't figure it out.

J is 13.5mos old and has been sleeping in her room since about 6.5mos or so. She dropped her early morning nursing session shortly after she moved into her room and usually sleeps all night long unless she randomly poops or has a tooth breaking through--Tylenol or teething tablets usually do the trick. About a month ago or so, she started waking up between 1230-230ish. We immediately rushed in there thinking it was teething/growth spurt/poop/hunger...but she would get so upset and just lay her head on my shoulder or husband and go right back to sleep. I figured maybe she was having bad dreams. It was a quick wake up and she'd go right back down. A few days later it became more often and now it's every single night. It's not teething (no swollen gums, extra drool, etc), she never wants milk or water, her diaper is always fine and she wakes up ANGRY...like she's throwing a horrible tantrum. The last few weeks we've tried letting her fuss but now she stands and jumps and I have to watch her on the monitor cause I'm afraid she will bang her face/head on the crib railings. My husband usually goes first and can get her back down but 2 minutes after she realizes she's in her crib, the cycle starts all over again and she becomes even more upset. I break down and go in and she immediately lays her head on my shoulder and I rock her. I will rock her forever and slowly put her back down and can't even make it out of her room before she wakes up again screaming her face off. I am so tired and so is my husband. We've had a lot of stressful events in our life over the last month and a half and I'm wondering if she's sensing that? Last night after trying to put her down for over an hour between the two of us, we told her we loved her and walked out. She screamed and jumped in her crib for about 45 minutes before laying down. There are hardly any tears involved in this whole process...it's all screaming. Any ideas/suggestions/tips?