My mom is making our relationship miserable

Ever since my fiance and I got engaged and have a baby on the way my mom has been making our relationship miserable. She brags about how she has a grandbaby on the way and brags to people how much she loves her son in law, so there is nothing she’s ashamed about.

Ever since the engagement she is always sticking her nose in our relationship, him and I like to keep things between us two so it’s really bothering us. When we get into arguments we just like to talk it out but my mom starts interfering with it which ends up setting us both off. She has even gone as far as telling us when to hug and kiss each other, she’ll be like ‘go give her a kiss’ out of nowhere and we really don’t like this.

We have plans to marry in September and my mom is making this tough, I tell her to just keep her nose out of our relationship and she refuses. Her and my father have a tough marriage, they fight all day mostly due to financial issues because they are both laid off. My mom is paying all her attention to our relationship and not her own, it seems like shes so unhappy with hers she’s trying to make ours the same way, I don’t know…

How can I stop this? I really feel this is happening due to her own relationship problems but she really needs to just let us do our thing, him and I barley ever argued before and her always getting in our business is causing more arguments than ever. Him and I have talked about this together and agree something needs to be said to her to make her understand. We are both mature adults and had a perfect relationship until she got in this, I don’t even know where it came from, she was never like this till the pregnancy and engagement. Jealousy maybe?

What can I say to her that wont hurt her feelings. Something has to be said before I end up lashing out, I cant handle it.