The reality is adding the stuff Goldie advised to your routine will help you immensely. Running uses most of the body, cycling depends on the type of bike to what gets used, adding crunches and nothing else to this presents a potential though far from major risk.
The abdominals are one of the major postural muscles and form one part of the group now recognised as 'the core' which is basically everything around the midsection, front, back, sides and internal. Imbalance here will affect posture and overtraining the abs without matching it on the lower back can, if taken too far, cause lower back issues and the delightful rounded shoulder posture which is appealing on no-one.
Balance is key in so much of health and fitness. To burn fat you want a balanced combination of aerobic and resistance training, circuits etc. do both while you may prefer to do them seperately by doing running and cycling for aerobic then resistance work seperate.
Gender is one of the least important things in regards type of exercise to do. There aren't enough muscles controlling the things making our genders apparent to be worth worrying about. If you go flat out heavy you will gain power, 6 to 10 build more muscle mass, over 10 more endurance, ridiculous reps will cross over to stamina.
The time gender comes into play is the effect, being female you could train at max in the 10 to 6 ideal body building range alongside me as a rather pathetically ectomorphic male and still not gain muscle as fast unless you were incredibly genetically gifted to gain or were supplementing your hormonal disadvantage. Forget any of the stupid myths that touching a dumbbell will turn you into Arnie. Consider the main group of women who use weights that people don't think of are bikini models, they know it's the only way to give their whole body the toned look that they need when exposing that much flesh, generally in the endurance range 10 to 15. That is what adding Goldies recommended additions will actually be doing for you.