Lack of Interest
The sure fire way to tell if a woman has a low libido is if she is not interested in having sex. If she blatantly says, "I do not want to have sex", or rejects any sexual advances, there is a big possibility that she is uninterested.
Lack of Response
We all have our "spots" that if touched, caressed, or even blown on, will drive us wild and make us darn near lose our mind. For some of us it is the ear being caressed seductively by our partners tongue and for others it is the gentle stroke of a finger behind our knee. If these infamous moves produce nothing more than a hopeless sigh followed by a rolling of the eyes, chances are, a low libido is the cause.
If a woman wants to engage in sexual activity, she will make herself available to her partner. Whether it is making sure the bathroom door is left open as she takes her evening shower, or calling for him as she sits on the bed clothed in nothing but a bath towel. On the flip side, if she is not interested, she will be sure to avoid him at all cost.
When you have been a couple for a while, there are certain activities that you know will lead to sexual intimacy. They could be a nice romantic date, watching movies at home, or even baking chocolate chip cookies (don't ask, some people have their moments). If a woman begins avoiding these activities that she once loved so much, she may just be trying to avoid engaging in sexual activity.
Mood changes may be more of a by-product of physiological changes in a woman. A woman's mood changes may be a result of changing hormones or conditions such as depression. The side effects of these physiological changes are often times a low libido.
A low libido can be caused by medical conditions or as side effects from medications. Other reasons could be attributed to lack of sexual stimulation and feelings about the partner. Exploring new ways to sexually stimulate your partner could enhance the low libido. In addition, it may be as simple as a couple revisiting and re-examining their relationship and going back to those things that drove them wild about each other in the first place.