What to do about my so called 'best friend'?

[💋Sammie💋]

Okay, so there's this girl (Maria)that we have been friends since 3rd grade and best friends since 4th grade. There is this other girl(jess) that has been my friend since diapers because our parents our best friends. Jessica doesn't like Maria and Maria doesn't like Jessica. Jessica is in 5 grade, she's supposed to be in 6th but she got held back for moving around a lot, maria is in the same grade as me(7th) and we have all of the same classes for 2nd semester. In the beginning of the year me and maria drifted apart and she called me a slut and a bitch, so we stopped talking for a while. So last week me and maria made up and we've been talking a lot and we have been trying to mend our friendship back together. Jess found out that me and maria were friends and she called me two faced, etc but at that moment she didn't care that much b/c we were having fun. Then last night on Twitter, she left me this message, (cope and paste)
" Don't talk too me no more im so piss off at you and i dont like it when ypu are two face HINT HINT how can I be friend with you"
What should I do? Jess has been my friend since I was 1 year old, but most of the time I don't like her b/c she has a horrible temper and attitude. Maria is my best friend since 4th grade and we had one little fight and now jess is made. Every fight friends go threw makes the relationship stronger! Maria always has my back, super nice unlike jess , but she cares about what ppl think and she can be a real bitch when she's on her period. What should I do? Thanks for reading and answering this!!
***Maria and Jess aren't their real names!! I just used it not to share personal info!!! ****

[sunny]

Just bring J and M together, sit down and talk. Tell them they are both very close to you and you need them to understand that you want both of them in your life because both of them are important to you and you don't want to lose your friendships with them over someone else. Tell them that they don't necessarily have to like each other but for you at least try to get to know each other first & spend some time together, like hang out together.