Strictly speaking, you can do anything with enough money, but to install auto locks on a car that doesn't have them originally won't likely be worth the expense unless you do it yourself.
Can you do it yourself? Not to be sexist but a lady who has the dough to buy a new car isn't likely to be sufficiently mechanically incllined, nor have teh tools, to do it. You should get the car outfitted the way you want it in the first place.
In the end, suggest you or your assistant clean the car very nicely inside and out, polish and wax, detail the heck out of it and sell it yourself. Use the proceeds to buy the car you actually want, next time.
You can try get a trade-in value from the dealer and see what the net cost will be after trade-in and purchasing the new car. That's the real cost of the deal, and it won't cost anything to ask. But you should be prepared for some hard negotiating.