Weddingbee boards

So a few years back a cousin of mine got married.  We aren't exactly super close, but we aren't distant either (make sense?)  She lives out of state and was at my house about 8ish months before her wedding, she mentioned her husband having more groomsman than her bridesmaids.  My grandmother suggested she have me in her wedding, I was at the table during this discussion so I feel as if she felt a little pressured to have me in.  Or figured what the hell, it's not like she had to pay for much for me to be in it and why not make things even with her husband.  So here I am, recently engaged and discussing bridesmaids with my mother and sister.  I only want 3-4 people as my bridesmaids and I didn't include her in on it.  My mother and sister suggested that its only right to have her in it because I was in heres.  I don't want a big bridal party and my fiance won't be having many either.  We mainly want those who have been there for us to be standing up for us.  Thoughts or suggestions??