Choosing Bridesmaids

I am having trouble deciding who will be my bridesmaids..

Aaron is going to have 3 groomsmen.

Most likelyI already have 2 decided. My maid of honor -my best friend Maya and my sister Jennifer. I maybe want one or two more.

Although my mom says I HAVE to match how many Aaron has.

The problem is who do I ask?

I have one friend that kind of assumed she would be a bridesmaid...

However, I was disinvited to her quickie wedding in Reno. I was going to go, then she decided to go a day early and just elope. Then I find out four months later, that her ENTIRE family and a few of his friends went. So I'm still a little annoyed about that.
Plus I hate her husband. He's a jerk and I dont know what she sees in him. Considering he's a junkie meth addict who fathered a child with another woman while they have been married.

Plus, She's done a lot in the past that annoys me. Like inviting random people over to my house or wanting to come stay the night and then disappearing before the night is over, like I'll wake up and she'll randomly be gone. Personally, she's a lot of fun to be around, but I dont think she takes my feelings into consideration.

I have some other friends, that I haven't really hung out with a lot because either we just lost touch, or they got full time jobs or go to school full time..etc.
I also have some friends from Sacramento that I dont see as often, but I used to hang out with all the time.I just don't know what to do.. or who to ask. I was thinking about just asking a few of them to see if they would be interested in being in the wedding. I know it can be a little expensive and I'm not sure all of them can afford it.

I was thinking of saying - the dress would probably be about 150 and that doesnt include any alterations. I'd love you to be in the wedding, but would understand if you couldnt afford to.

This sucks. Its hard to choose.