My question is....why make the suit have boobs in the first place? That seems like an odd place to focus any efforts.
As others have noted, Patterson was strongly influenced by an account given by a Mr. Roe of surprising a female bigfoot who then gets up, walks away, turns back, and then wanders out of sight into the woods. This is evidenced by the illustration in Patterson's book, which is, uh..."swiped," they call it in the funnybook business, from an earlier drawing in a men's adventure magazine. As for where Roe got the idea, well...you know, boobs. I notice whenever men travel into the wild, be it by land or sea, they come back with tales of strange creatures, many of which have boobs. Plus, "guy surprises lady in the bushes," that's straight out of Cap'n Billy's Whiz Bang, and that's the level we're dealing with her, with these guys.
Plus, a female Bigfoot, accounts for why your "creature," isn't quite as big as they supposedly are, and lends a whole level of, like...biological credibility. I mean, with boobs you're most of the way towards an animal, if you see what I'm saying.
There's also, and here we're getting away from what is known and on into just me talking, but...every monster movie needs a monster and a girl, and Roger only had the budget for one actor. Plus I can get all...Alan Moore-ish and mention one legend of the patty-suit has its origin in a "girl to gorilla" act, so it's just like, whaddyacallit? cosmic patterns of synchronicity an'at.
I saw this Bridgette Bardot movie where she plays this masked burlesque dancer, and I get sort of the same vibe from Patty, where she gives us a little glimpse of this, and takes it right back, and a glance at that, and hides it again almost immediately, and then, finally...we get one, short view of everything we came to see...right before she disappears behind the curtain, is what I'm getting at, and I suspect Roger has studied this kind of theater, those sorts of entertainments being popular among the kind of fellow who has no steady or obvious means of employment, and so of course there are going to be boobs.