If you don't want her to drive all the way out to you- drive out to her.
I think this conversation would be best had in person though. if she has to drive out to you, first tell her that you'd like to talk bout your relationship and how it's going.

First though, you need to decide the outcome of this conversation. I think the most important things to focus on would be the drifting apart and the arguing. do you want to keep dating her or would it be better to breakup how can you (and her) fix the issues in this relationship? what if she disagrees? are there any other issues that might come up on her end? how will you deal with those issues?

So your issues (assuming yo wish to work through it) are drifting and arguing. (intimacy can be fixed after the drifting and not much can be done about routine, so focus on the drifting and arguing) I think If I picked one the most important thing to work on would be the arguing, as that doesn't help with the drifting at all.
arguing: You mentioned that her anxiety can lead to arguments, so the key to at least beginning to argue less may be to understand more about her anxiety and her needs surrounding it. Ask her about her triggers and what you can do to help in a situation. most importantly- talk about IF she needs help in a situation. (eg, you say you feel the need to take control of small situations like speaking to store employees. Does she need you to do that or does she feel it's better to push herself through it?) Most importantly, ask yourself if you can deal with her anxiety. It's not a bad thing if you can't, just means that you're not right for each other right now.
drifting: How can you grow closer? is there something you can bond over? thinking back to the start of your relationship and what brought you together then may give you some ideas.

If you decide to break up, it would not be considered to rude to do it over the phone/skype if the only other option is to have her go far out of her way just to get dumped. (seriously, the amount of guys who decided to dump me face to face when I had to rearrange everything to see them- i would have even been fine with a text over that!) there are a few things you can do to minimize the emotional impact of the breakup.

1- don't tell her you love her. that just confuses things.
2- she'll want to know why. State your reasons (arguments and drifting) clearly and concisely.
3- don't add to the emotion. She may be upset, and may say hurtful things while she is or bring up past arguments or more issues in the relationship. Don't argue with her. Insulting back will only make emotions run higher and relationship issues don't matter. you're breaking up. they are nothing to argue over(you can talk about them if you like, just don't argue over them). one party staying calm will limit the emotional response of the other.
4- no backsies. If you break up you break up. no prolonging the relationship only for it to break up next week.

note: her anxiety may be an issue. If she has an attack or something, calm her down, but still stick to the no backsies rule.