So, should you worry about what this ex-friend is saying behind your back? Should you try to get in your mutual friends’ and neighbors’ ears and convince them of what a selfish freak she can be, how her view of you is inaccurate, how angry and disappointed you were when she didn’t step up and notice that you were having a rough time yourself? No. If they have brains in their heads, they can see very clearly that she is immature and vindictive toward someone she previously treated as her closest friend. It should be obvious to them that her reasons for icing you out are weak at best.
And if these mutual friends don’t know that, or it’s more convenient to just keep the peace with your needy drama queen ex, or they actually find her tirades against you convincing, then you don’t need them in your life anyway. You know you’re not a bad friend.