No you are not a bad Mum, not at all. What you are doing is trying to figure out what is best for Cali, and anyone trying to do the best is a sign of being a caring piggy-Mum, certainly not bad.
I had a piggy named Snowball and she didn't fare well living in a herd. I introduced her and she was nervous and ended up fear-aggressive, her chattering of teeth at the others eventually sent the entire herd off into aggression and I had to remove her. This was a failed introduction.
Back on her own she was more confident and was quite a 'people' pig. After a few months I tried her again, and again she was nervous but there was no aggression from her, just lots of running and hiding. She eventually calmed down and lived with the herd for a year until she started getting aggressive again.
Having removed her for a second time I bonded her with a boar and she was clearly very comfortable with him. Though she had plenty of attention from me it clearly wasn't enough, she had become restless and looked a little lost somehow, and was truly happy with her boar-friend.
This showed me that even though she appeared to dislike piggy-company she actually just needed the right one for her.
Oreo was another piggy I had who needed boar company, not other sows.
Obvioulsy my Snowball had a different character to Cali, with Snowball being more submissive (her's was fear-aggression) and was not really one to mount.
However I would have thought that yours is another case of not finding the right friend for her. Some piggies are not fussy, they are easy-going and will accept just about anyone, whilst others need a certain personality to click, and some prefer one sex to another.
I agree that taking her bonding to a rescue would be a great idea for her, and they will also supervise the bonding and will know which behaviours from her are likely to be temporary and which ones are signs that dominance may go too far. I always found intros stressful and often it looks quite bad when it's actually quite normal and as I say, temporary. However drawing blood on the other was clearly a step too far. As a rescue is likely to have done many intros, they will helpfully have some idea of likely compatible matches for her personality
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