I just thought if I could put something in place that says she can’t come within a certain distance of the house, or contact me, it might draw a line in the sand to encourage her to just stop and move on.
You say she has no direct contact with you though, so what contact would you be looking to stop?
You can block her number/socials, your partner can tell his children not to pass messages. Unfortunately she is (however unwarranted it may be) entitled not to like you and tell her children as much. Being a twat is sadly not illegal :-(
You can't stop her coming near your house without very good reason. You're not in danger from her, you just don't like her.
However, you could report her to the police for harassment, if you feel that is what her behavior amounts to (see bottom of this post for the definition).
As a softer option, you could pay a solicitor to send her a letter, if you think that would be enough to draw that line in the sand you mentioned and scare her off, as it were.
Bare in mind though; is it likely to have that effect, or will it simply escalate things? From what you've described, it's unlikely the police would do any more that talk to her at this stage, which could embolden her depending on how committed she is to making your life difficult.
At the end of the day, your partner does still have to co-parent with her.
"The Protection from Harassment Act 1997 indicates that someone’s actions amount to harassment when they make the victim feel distressed, humiliated, threatened or fearful of further violence. The main goal of harassment is to persuade victims either not to do something that they are entitled or required to do or to do something that they are not obliged to do. Actions listed under the Protection from Harassment Act include, but are not limited to:
phone calls
letters
emails
visits
stalking
verbal abuse of any kind, including on social media
threats
damage to property
bodily harm
Such actions amount to harassment when they occur more than once."