Bridesmaid Trouble...

You seem to be toying with the idea of having four bridesmaids, but how would your FH feel with you going against what you both already decided? If you feel your SIL will be a better fit, go with that. You will never be able to please everyone. If she is truly your friend she will understand. Good luck!

I would have a nice call to her and talk about happy things. Explain to her that you have to limit your side of the wedding party (cutting it down) and that you need to include your sister-in-law. Tell her that you hope she will come to the wedding. I think that most people would be offended if you didnt acknowledge the change in plans. People get excited and think they want large wedding parties and then time changes the relationship. Just talk to her or ask her to do something like a reading if she wants to be part of the ceremony.

Jeez, some people are needlessly rude on these forums!
Go with what feels right for you. If having minimal communication with each other feels like the friendship has died a bit for you, then that is YOUR feelings. Just because others wouldn’t feel the same way doesn’t mean it’s right or wrong. Absolutely do not do anything out of obligation, i think you will just regret it later.
Do you think the two of you could have an honest conversation about it? Like without it turning into a fight or something? Last year my friend was in a wedding with a friend who she had fallen apart from. She dreaded every part of the things she had to do for the wedding, and seemed to resent the friend for having to be a part of it. I sometimes wonder if the bride was thinking the same thing, but was afraid to speak up the way you are feeling now. I think if they had just had a conversation about it, they might have saved each other some grief!

I am not sure how long you have been friends, but if you considered her in the first place, there was a reason why. Long lasting friendships go through ups and downs, times where you chat everyday to times where you go months in between. These are the friends that you end up having for life. If she is someone who is important to you, and that you would want to stay in your life then I say go with an uneven number, or maybe find a different special roll for you soon to be SIL. True friends are hard to find!

It seems like she hasn't wanted to be too involved in your wedding thus far so... I don't think it's rude to not have her in the wedding. The thing is, if you have her in the wedding she's not just standing up at the alter, she will be in ALL your wedding party photos forever. So if you don't think you will be friends with her forever then.. I'd just not have her in the wedding party

I'd be hurt if I was your friend. It wouldn't be a relationship end-er, but it would definitely cause tension for a good long while.

I can't do uneven sides. I know a lot of people say you can but that's something that I can't do. Personally I dont like the way it looks. Its nothing against other ppl that do, it's just not my thing.
I would go with your future sis in law. It sounds like you're really close. Maybe you could have your friend do something else? If not, explain to your friend that you just haven't felt very close to her lately and haven't spent time together. One time in almost half a year isn't much at all. Depending on your friend, she may understand. I had a friend I cut out of the wedding and she said she understood and was just happy that I found someome who made me happy and was invited to be there.

I had a situation similar to this, I had a lot of back and forth with the position of MOH between my best friend, who I'm not friends with anymore, and my soon to be SIL, nothing was ever decided after my BFF and I went separate ways, but my FSIL attempted to put herself in that slot as a filler, but I'm not that close to her, and she doesn't participate a lot in wedding planning, so in the end I decided not to have a MOH, but I was able to talk to my FSIL and tell her just that, that I'm not filling the position with anybody. She was completely understanding. Since this is someone that you don't have a close relationship with, I don't see it being a big deal, especially since you don't talk much anyway. If you mentioned it a WHILE ago, she might not even remember! I totally understand wanting an even lineup. My FH and I have the same OCD moments when it comes to the symmetry of it all

Just put the sister in law in, and tell the other one you are really sorry, but it would offend FH if you didn't put sister. Hopefully she understands.

You should also consider how people react to weddings. I recently got engaged and most of the girls aren’t as crazy excited as I expected them to be. Then I realized one of the reasons I adore them is that we just love each other where we are at.
Also be honest with her. Express you feel a disconnection and see what is going on. She might think things are fine or she might just busy with her own life. (One of my bridesmaid’s father past away the day before I got engaged. She needed her space for her).

I also thought even numbers were a must but we have an odd number. I’m just having my MOH walk solo. Best of luck!

Some people are really sensitive. I see so many people on WW and otherwise saying dramatic things like, "I'd end the friendship." Well why? Things change, things happen, it was never even a commitment. I don't think, by the sounds of it, this girl would be all that surprised if you never officially asked her to be your bridesmaid. You have barely talked to her/hung out with her, why should she assume she's going to be that big of a component anyways - that'd be weird. I think a lot of girls just have the dream of being a bridesmaid, and get offended if they don't get to be one - Even though it's not about the bride that they're supporting.

Anyways, I know it's nerve-wracking. I have a big mouth and I'm in a similar situation. But it's your big day, you only get to do it once, so do it exactly how you envision it. It sounds like you have a 3rd girl whom you are very passionate about being there, so don't NOT include her, ya know?