I can tell you that some women do better with a female trainer for various reasons.
However, in my experience, female trainers tend to take it much easier on their female clients, and are often times are what I term "over appeasing". Meaning they won't tell you things that might make you not like them.
Now I realize my views are likely to incite some negative response, but it's something I've always found as a stereotype.
My advice is to be aware of what kind of trainer is going to work best with your personality type. There are some female trainers who are outright ball busters. I've worked with a few that made bodybuilders want to curl up in ball and rock back and forth crying.
However, the main thing you should realize is that a trainer sees you as a client. And only a client. They don't care if you are fat, stink a little, have perfect make up or not. They are not there to have sex with you or date you. They are there to help you get fit.
Find someone who specializes in your training goals and has references or at least photographs of success stories they trained. Discuss time lines and goals, and willingness to set up a plan.
Often trainers will simply use a standard print out based on the same work out they give everyone else. If you have specific goals, then tell them you want a program tailored to those.
Don't judge a book by it's cover. Just because a trainer isn't ripped or musclebound doesn't make them any less effective. You wouldn't refuse to see a heart surgeon just because they smoked would you? You'd be more interested in their success rate. So go with that when making a decision.
One last thing... beware of the bulk packages for training services. Usually they are a scam. You'll never use all 10 sessions. Usually to get started people need 3 sessions. One initially, another a week later to make adjustments and another a month or so after that to switch up the program. After that you pretty much don't need to see a trainer until you have to switch things up again (which is every 6-8 weeks). So be careful and don't waste your money.
Remember that the trainer is not there to do the work for you. That only you can make it work. They are just there to show you how to do it.
A common misconception is that getting a trainer will sort out all your problems and you'll see results quickly.
Before you spend money on a trainer, you should get your diet and water intake dialed in and correct. Because until you do, money spent on a trainer is mostly wasted.
Trainers are NOT nutritionists or dietecians. If they are trying to sell you on supplements: RUN! Any reputable trainer will tell you that for general fitness and health nothing more than a standard multivitamin is needed.
If they try to sell you on fat burners or any other pills, just say no. They aren't qualified to make those judgements and it's not part of our training in any of the accredited programs.