Is this weird and would you be offended?

I'm 8 weeks pregnant and a UK size 16. My mother in law offered me some of her old clothes when I get bigger and she's roughly a size 26.

I would feel a bit weird wearing my MIL's hand me downs and I have to dress smart for work. The size issue bothered me as well as I felt like she was saying that seeing as I am already on the big size that I will probably go up 10 dress sizes anyway.

Am I over reacting?