Is there anyway to know if I am ethnically jewish if my mom was adopted?

I am blessed to have many Jewish friends and I feel so connected to them in energy, humor, interests and in conversation. My friends always ask if I am ethnically jewish but I have no idea. My mother was adopted and every time I ask her questions about her biological mother especially when asking about being ethnically Jewish, she gets annoyed or something. Maybe I just wish I was jewish because I have never met people that I resonate with as deeply as my jewish friends. After my mom got upset with me about asking about my grandma her name was/is Deborah Neighbor – she gets pissy. And today it sent me over the edge and I cried for hours I feel like my mom is lying to me.