Joint Baby Shower with sister.

So I am pregnant with my first baby due August 2nd and my sister is also pregnant with her 4th also a girl. Her youngest is 4 years old and my mom is wanting to throw her a shower as well as mine. Is it crappy of me to make it well known that I do not want a joint shower with my sister?? It was difficult for me to when I found out she too was pregnant because she already has three by three differ t men and this is my fiancé and i's first child.