Does Having Other Children Make Birth Mother Less Eager to Make Contact?

I recently located my birth mother by opening my records and finding her on face book, turns out she has 7other kids- 6 older and 1 younger that she raised. I was surprised that I felt less excited about meeting her then I thought I would, more excited about the fact that I have siblings- I was raised an only child. The only reason for this that I can think of is because I had a great adoptive mother, so that mother relationship isnt lacking for me, but I have no adoptive siblings so that is lacking. My question is, does this work the other way around? Maybe my birth mom isnҒt interested in communicating or meeting me because she has so many other children to fulfill that need for her??