not intended to offend any women...
Considering you did say she says the engine cuts off, when was the last time the engine was tuned up? It may be just running poorly until it warms up. Putting in in gear and putting resistance on the engine may be causing it to stall out. If it's been forever since the last tune up, she should have a tune up done.
new air filter
new spark plugs
new spark plug wires
change oil
change transmission fluid filter
new fuel filter
All of those should help the engine run better, which may solve the problem.
BTW, every woman I know (girlfriend, mom, aunts, female friends, etc...) couldn't tell me when the last time their vehicles were worked on if their lives depended on it. Their boyfriends/husbands keep up with it for them. THAT is why I mentioned the 'she' thing. NOT to offend any women who DO keep up with that stuff, just saying that all women I KNOW do not.