Sorry this is a long story but I'll put a TLDR at the bottom:

A few months back, my husband's grandmother passed away. She lived overseas, close by to where my husband and I live , so a lot of family from america flew in for the funeral. After the funeral service, I heard my mother in law talking to my husband, asking him if I would consider escorting their 13 year old daughter (his sister) back to america, since she cannot fly alone.
The Mother was flying to another state back in the US, where her sister was suffering from cancer and not doing well (the father travels a lot).

My husband said absolutely not. He did not like being separated with me for long periods of time, and I have anxiety and depression, and he did not want my condition to worse in unstable situations. He did not want me to be 'used' for whenever his parents needed something done.
I spoke to my husband later, and said I would be honored and flattered to have his parents give me such a major task to do, and to help his mother out during these hard times. Her mother just passed away, and her sister was ill, I wanted to help however I could, I wasn't working at the time and didn't mind helping out. Eventually I convinced my husband and I packed my things to go with his sister.
Before I left, my mother in law approached me and asked me to make my sister in law breakfast each morning, and dinner, give her medicine if she's sick, and take her to the doctor and after school activities. I agreed, she also warned me NOT to act like a parent, just a helpful adult. So I agreed to that as well. 

When I arrived in america, I got very ill, so did my sister in law. We were both so sick, we lost our voices, and it hurt to speak and swallow. Despite this, I still got up at the crack of dawn and helped wake her up, and made my in law breakfast each morning (we ordered out for dinner). 

Meanwhile. At their home, my husbands brother, (18) was living at home, played video games all day, and went to college and did homework late into the night (whatever floats his boat), but sometimes would throw loud parties in the middle of the house while the sister and I were trying to sleep.  I would sometimes stay up late at night with him to help him with homework and give him tea to help him keep going. But due to his laziness, and the sister's illness (and I suppose age), neither of them cleaned up after themselves. So I did my best to clean the house each day, do their laundry, ect. On top of this: the family had rented out their home the previous year, and only started to slowly move back in, so the house was a WRECK of boxes and items strewn everywhere. I also spent a lot of time trying to clean the home as best as I could, and organize, although it wasn't easy. 

At some point, my depression catches up with me, and I begin to slow down in pacing. I can't clean up as well each day, and I struggle to make dinner for the daughter and order out more and more often. I was told when my mother in law would arrive, so I decided to pull myself together to clean the home as best as possible before she arrived. 

She arrives earlier than I expect and explodes. 

She begins to freak out the kitchen isn't clean, that my sister in law hasn't been eating sufficient dinners. That the place is a wreck. She screams she is too embarrassed to call cleaning people because the house is so messy. I apologise and say I was doing my best to keep up each day, but it was difficult when I didn't get any help. 
Mother in law rolls her eyes, and says, well of course a thirteen year old isn't going to clean up after herself, and an 18 year old isn't, but a 27 year old woman!? She tells me to my face she is concerned for our future family, how will I be able to keep up with it? How will I be able to manage it? I am stunned, after everything I did for her family...none of that counted. At some point my explanations turn into defense and we begin arguing, and I say, "I have been doing so much for your family, why does none of that matter to you?" and she freaks out I said, "YOUR family" as though it wasn't my family, but what I meant was her children. 

Eventually I tell her I am going to stay by my sisters and begin packing my things.
For some reason, my mother in law believes I left, and she begins trash talking me to my father in law. 
The house is a wreck, food she bought isn't being eaten, is she really the best person for their son? Is he really happy with her? She can't believe a 27 year old woman can't keep the place together, and how she said she was taking care of 'your family' as though it wasn't hers!
I come down stairs and tell her I heard everything and we fight again. My husband gets on the phone and calms his mother down, and after talking to her for awhile, she cries and apologizes to me. I tell her it's okay, and I apologize to her as well, that I only meant to help her (I figured with her mom passing and her sister being ill, it was a lot for her all at once). 

The next day, staying at my sisters, I buy my mother in law a gift to make up for what happened. My mother in law says I didn't need to, but accepts it. 


Anyway, fast forward to now: I am extremely destroyed by everything I heard her say. I haven't been eating well, or exercising like I used to. I keep wondering if she's right. Maybe I'm not the best person for my husband, we love each other so much, we would call each other each night while I was in america. But I wonder if I'm not good enough for him. For a future with him, to hold together a family. I keep thinking she was right. Despite my good intentions, good intentions aren't good enough: it's what you are actually capable of doing, and I don't think I am capable. 
Am I the asshole for taking on something I thought I could, but couldn't handle?


*TLDR*:
Escorted my sister in law back to America, was in charge of taking care of her, I did, and also their son, neither of them helped clean or do laundry, so it was on me to do it. I couldn't keep up and my depression made it harder, mother comes home and is pissed and tells me I'm not good enough to hold a family together and may not be good enough for her son. 
Am I the asshole for taking on something I thought I could, but couldn't handle?
