Honestly, I do not think that her retirement will have a negative or detrimental effect on future female drivers. I believe she had a very positive effect for them, opened doors that may have taken allot longer to open, had she not been in racing. This was due more to her popularity and her name recognition, than her talent.
I believe her inability to attract another sponsor was a combination of things. GoDaddy was with her from the beginning and they would have stayed with her, I believe, had they not had the change of ownership. But a couple of things worked against her, attracting a new sponsor. One, due to the economy and it's VERY SLOW recovery, sponsors became far harder to find (still a problem) as they just didn't/don't have the cash flow that they had in better days. Full season sponsorships seem to be a thing of the past, unless there is a tremendous recovery. So that is not specific to her, everyone else is having that same problem, even the TOP drivers and teams in the series -- witness Jimmie Johnson, a 7 time Series Champion, that just lost Lowes Sponsorship.
Another thing that worked against her. She did not produce the results. She was in top equipment, but did not produce as she should have, witness, Aric Armirola, he has already shown better results in the same car, this season. I do not believe that it is because NASCAR is still a "good old boy's club. She was a good driver. The problem was that she came from the wrong racing background, the WORST background to come from, to be successful in stock car racing. She came from forms of racing (road-racing and open-wheel formula car) that have little to no transfer skills that can apply to stock car racing. In fact, everything that she learned, worked/works exactly the opposite of the way things work in a stock car. The problem was compounded by the fact that she spent practically no time in the Xfinity Series, even though listed as running a season there, in reality, she only ran a handful of races, then the next season, she went directly into the Cup Series, in one of the top team's equipment. She WAS NOT ready for that jump, did not have the experience in stock cars. She should have been running every K&N Series race that she could, as well as running Xfinity and ARCA Series races, to learn how to drive a stock car. She needed to learn the "feel of the pant's" on how the car handles, how to set up a stock car and how to communicate what the car was doing to the crew chief. She did not have that and it SHOWED! She should have run what I said above for at least a full season, before she went to the Cup Series. Her lack of seat time in stock car series below the Cup level pretty much doomed her to being a mid-pack driver. That is nothing against her, just the circumstances that she faced, due to the lack of experience.
Back to the topic question, her retirement is not detrimental to future female racers. Presently, there are several young female drivers working their way up the ranks in the K&N Series and one, a rookie, in the ARCA Series, that looks to be a future star. They should do well in the future and likely will do allot better than Danica Patrick did in NASCAR, simply because they are coming up in the proper background, that will lead to success in stock cars. They are learning the basic skills that Danica never developed. But, her being NASCAR, none the less did help open the door for these young female drivers.