Are female Democrats held to higher ideological standards than male Democrats?
Possibly, but you're cherrypicking. Also, your examples don't really make the point.
Blanche Lincoln is a staunch Free Trader, known for publicly opposing a number of progressive initiatives including a public medical insurance option and the pro-union Employee Free Choice Act. Obama had become very unpopular in Arkansas by the time she ran for re-election in 2010, so even her pandering to the conservative Democrats didn't help her survive the challenge from Boozman.
Natalie Tennant seeking to distance herself from Obama in 2014 should not come as a surprise. Nor should her defeat at the hands of Capito (a female, by the way.) Comparing her in this regard to Manchin is not really appropriate since he was up for re-election in a presidential election year. Turnout is higher in 2012 than in 2014, and the more gritty voters are better represented. Also, she was running for election in 2014, whereas Manchin was running for re-election in 2012. Not really an apples-to-apples comparison.
Grimes won more than 3/4 of the primary vote in her bid for the nomination to replace McConnel, so at best she is an exact counterexample of what you're trying to point out.
The anti-war left has good reason not to get excited about Hillary Clinton, a power projectionist from 1998 onwards. Clinton has plenty of neoliberal credentials, and this should not be surprising since she learned from her husband, an expert at triangulation. Obama, on the other hand, has pursued a rather progressive agenda. (Of course, he also supports the sort of post-apocalyptic Orwellian society being espoused by Democrats and Republicans, but his left-wing critics haven't given him a pass. You'll find plenty of outrage on the internet regarding his drone policy, for example.)
There are also a number of counterexamples who show that conservative female democrats have done just fine. Ann Richards not only defeated her primary opponents in 1990, but went on to become governor of Texas from 1990 till 1994. The Blue Dog Coalition has had a number of successful housemembers over the past several decades who are female. The current governor of New Hampshire is a female Democrat who has transformed from a tax-and-spend legislator into a fiscally conservative budget hawk. This will earn her criticism from the left, but not because she is a female. I'm sure you could compile a long list of successful conservative female democrats. In fact, the first female Governor in any state was a conservative Democrat, as was the second, who served for two terms.
