How lesbian sex can be protective?

I'm not a lesbian but if you are getting several infections, it may not have much to do with sex at all. Talk to your doctor, as it might not even be infections. Maybe you are getting an allergic reaction to your detergent or something like that.

It's possible, also, if you are using sex toys on each other, that they might not be perfectly clean every time. Check the manufacturers' sites and find out how to clean these products. And if a manufacturer doesn't have cleaning instructions and won't answer emails or a chat session asking about how to wash the product, then throw the product away.

As for a 'glove', etc., I don't think a female condom will help you there, and this is not what they are meant for, anyway. I suppose one could slip a condom over a dildo, but you will have potentially have a reaction if you are sensitive to the lube or latex on the condom.

So - first - contact your doctor and start asking questions and to get them to investigate why you are getting persistent infections.