Generally speaking, therapists are trained to handle being told about possible attractions to them in a calm and kind way. I'm not sure about how well your therapist has been trained, but since you seem to feel so positively about her, I'm sure that she'll be alright, so you should be aright to tell her.
As for your sexuality, it's valid regardless of how they came about, trouble with your mother or just born that way.
I'm a baptist myself, and I tried to talk to my church about it when I started to figure out that I was pansexual (meaning I'm capable of attraction to someone of any gender), and they completely dismissed me and tried to talk me out of it, so I had a bit of an existential crisis over it, but in college I got to visit a really accepting church where I met a bunch of gay Christians and got to talk to the pastor about it, so in short, it's perfectly natural to be both gay and a Christian.