Question, should I befriend my husband cousin?

It's a cousin from his father side of the family
I really like her (as a friend of course) and wants to be her friend and we get along well but the only reason I don't really tried being her friend is because the relationship they have with my mother-in-law is so so, sometimes good and sometimes not so good.

For me I have a good relationship with my mom in-law and I don't want to ruined that.
Do you think becoming her friend would ruined it?

People from my husband family already knows we get along well but I keep my distance because I'm scared of the future 😔
I really want to be her friend though