Moving out from parents

Sooo, yesterday my partner messaged me and told me he’d been looking at houses in my home town (he lives in the city) and had found one for us to look at, so i said yeah we can go and look, I wasn’t really expecting much in all honesty.

So we went to look at it today and it was great and we’ve decided we’re going to have it, were over the moon and so excited!

The thing is.. I don’t know how to tell my mum I’m moving out? What do I say? I’m worried she will fall out with me... I am 23, just don’t want to ruin my relationship with my Mum :/