She’s looking to use it in my ass so it can be a quicker transition for her to use her strapon on me (Pegging). That way she can move right to it in the heat of the moment and not have to stop, add lube, put a condom on the strapon and then get to it.
The big baggy type might work but we never dispensed or saw them. Seems like mostly marketing by men who dont like condoms. The above is not how female condoms, most call them diaphragms, work. I did a clinical rotation in a Health Department years ago fitting them to women. Closes comparison I can think of is a stiff rubber ring about the size of a Pringles lid with a piece of condom like material stretched across it. They need to fit the cervix and smeared with spermicidal jel. It is a barier method. The penis does not go inside the thing, therefor useless in anal sex. Not effective against preventing Veneral warts or Herpes. Not a very effective form of birth control. Rarely used right. Disgusting part is they are re-useable.
You have the two methods of birth control confused. A diaphragm is reusable and is used as you mentioned with spermicide and then inserted like a cap over the cervix to prefent pregnancy as a barrier method. It is reusable and isn’t as bad as you think as the diaphragm is removed after sex and cleaned, Below is a picture of a Female Condom with is completely different and is NOT I repeat it NOT reuseable. It is also a barrier method but more similar to a male condom.
I have used them a couple time and always have mixed results... We have used them for both vaginal and anal (Both Her Receiving and Me Receiving via Strapon) and although the flip to action is a little faster, they are very thick and I think messy with the amount of lube on the outside.
I don't love condoms, but one thing I actually like about the male version is the slight tightness on the penis. Gives me a different sensation.