I feel so horrible......

Went to see my mum today and helped her out cleaning and stuff and I asked her if she wanted to come over to mine tomorrow to have some cake and stuff as it's gonna be my birthday and she said only if your boyfriend will pick me up and take me....
Maybe I'm over reacting but I live 15 minutes away from my mum I always walk there even though we have a car my daughters walk there too. One is 3 the other nearly 2.
Should I be pissed of or am I over thinking this?
I can't believe my mum would say something like this