How to show the financial means same for both the applications?
Do you need to show that the financial means are the same? If they are the same, great. If not, you can provide separate documents for both. Or say that one is supporting the other.
If I were to courier her my bank statements how old should be the statements?
Anything reasonable should be okay. For example, a month before the date you apply.
She also has bank account in UK which is just one month old while Time of applying , should she use that account?
If she had just entered the UK as a student and wasn't there before, then by all means. Even if she hasn't been there for that long, but it provides financial sufficiency, then yes.
Our Marriage Certificate is with her, how do I explain this dilemma to the Embassy?
Tell the embassy that she is a student studying abroad while you are being interviewed or in a cover letter. Get a copy of the marriage certificate to submit with the rest of your documents.
I just have tax returns of last two years.Is that okay?
Yes, that is perfectly fine.
IN GENERAL: Embassies just want to know that you are going to the place you say you are going to with the proper purpose. So, what you need to go in general, is provide documents that show that you are indeed going there to be a tourist, and that you have no intention to stay for a longer period of time. What may support this is having a job in your home country, or being enrolled for classes, or land, or other investments. This shows the genuineness of your intent to come back and really just go to France/Switzerland to go on a vacation!
I've applied for a lot of Schengen visas, and it gets scary at times, but it will all turn out okay! Hope this helps!