Not sure if you're going to answer bc it might be answered in the fic plot but...I noticed Mia has something acidic in her body, possibly uti, or am I reading too much into it?

It won’t be directly addressed on the fic, no. The tags will be respected, and they say everything is implied and it will remain that way. So I will clarify this for you here. TW:

You are very observant! Mia does have an acidic issue. Forced or rough penetration, rough contact, or prolonged distress can irritate or damage the urethra, making it more susceptible to bacterial infections. Any pressure on the bladder during the act can also lead to inflammation, causing post-traumatic urinary discomfort.