I believe they mean cum-inflation, which is basically what it sounds like, basically an excessive amount of cum stretch the womb or stomach past what is possible normally, as it causes bulging, some people may like to see that happen though, but knowing the infection system, it might not do well unless she develops an good immune system.
Now for the breast expansion, I would like to see Tali's tits get bigger and have a possible milking scene happen from a creature or person sucking on them, as my idea if you do have it happen is make being milked another source of income, of course you would need pills or something to increase breast milk productivity, and the breast size increase, but overall I say it'll be interesting, but in the end it's your decision.