Yes. I have that option but the default voice is terrible.
Ah, I misunderstood then because you asked specifically for a female default voice when the default was just that. Anyway, you cannot replicate this functionality by OXP. You can install sound OXPs (like BGS, which contains female voice messages or Halsis etc.), but those willl be just pre-recorded samples for very specific events in the game, which is not the same as a text-to-speech conversion of every message that is generated. You either get good quality samples for a few events, like hyperspace countdown, incoming missile etc. or you get less good quality text-to-speech that works for every game event.
I am not sure how it is done on Linux, but on Windows we are using a female voice which is not the same as the "ortiginal" espeak provided one. We have changed breathing and pitch and a few other things, precisely because the original coming from espeak was atrocious (yes, much worse that what we have now). If you are using that same modified voice and are still not happy with how it sounds, it is possible to modify it further, What you can maybe do is check the espeak-data folder of your Oolite installation and look inside the voices/!v folder for the file named f2. This is the female voice file we use. It looks like this currently:
pitch 188 228
formant 0 105 80 150
formant 1 110 80 160
formant 2 110 70 150
formant 3 110 70 150
formant 4 115 80 200
formant 5 115 80 100
formant 6 110 70 150
formant 7 110 70 100
formant 8 110 70 150
stressAdd 0 0 -10 -10 0 0 10 40
breath 0 2 3 3 3 3 0 5
echo 140 10
breathw 150 150 200 200 400 400
Does your f2 file look like this? If not, then you are probably using a voice different to the intended one and you could try to just copy/paste the above into the !v folder and see if it improves. Otherwise, you will have to do some experimentation on your own until you come up with something acceptable. If that is not an option either, then I am afraid you can only use one of the proposed OXPs, which will not be the same thing, as mentioned earlier.