Crazy ex

So my partner has been spilt up with his ex for 3 years now and we have been together for 2. We have a child together and we are engaged. But the whole duration of our relationship we have had issues with his crazy ex making fake profiles, sending me messages, calling and basically creating bullshit. She is over him, she's had boyfriends. I literally don't know what the problem is. We haven't heard anything for a year now. But we saw one of her sisters at the shops who literally followed us around with her phone up (obviously taking photos or videos). You would think they are little school girls, but no they are grown ass adults. Thank god our baby wasn't with us. But I am worried about the next time they see us. I definitely don't want them taking photos of my child. Any advice? 🤦🏽‍♀️🙄