This is Brittany's natal chart (alas, without a birth time) in the center, and the transit and progressed wheels have been set for around 8 am pacific time, when the 911 call was made. Several things stand out in this chart immediately: The moon in Aquarius was approaching a sextile to her natal Neptune and was nearly exact, as well as having just passed a square to Uranus. Transiting Mars is about a degree away from a square to her Sun, something that is made more profound by the fact that Mars stations to go retrograde today and its exact time of stand still was around 5:30 am today, not long before the 911 call. Saturn is also approaching a square to her Jupiter in Cancer and Pluto opposing it, but both have been happening for more than a few weeks now. An additional fascinating thing about this chart that is not readily apparent from the image is that her progressed Mars also stationed retrograde, just 10 days ago. This is a rare event, and may not signify anything much on its own, but coupled with transiting Mars doing the same thing makes one wonder. It is unfortunate that we do not know her time of birth, because I wouldn't be surprised to see stressful aspects to her ascendant.
Mars has a great deal to say about how one defends their boundaries, processes anger, and acts on their motivations, but it's significance in the physical realm can have a lot to do with our physical energy and our robustness. According to Eileen Nauman, an astrologer who is an expert at medical astrology, squares between Mars and the Sun can signify issues with the heart, such as heart palpitations, high blood pressure, or anything that causes stress (Mars) to the heart (Sun).* Brittany does not have this aspect natally, so it is less likely that heart trouble was a chronic condition but something that was triggered as transiting Mars' strength squared the Sun, and was then amplified by it standing still (stationing). Was something started 10 days ago (or earlier in the build up) as her progressed Mars also stationed to go retrograde, while squaring her own Moon?
EDIT: Today People.com reported an interview with Brittany's husband Simon and he did indicate that she had a heart condition:
"He added that his wife of three years did suffer from a heart murmur (mitral valve prolapse), which can cause fatigue, dizziness and irregular heartbeats – but is generally not life threatening. Murphy didn't require medication to treat it, says Monjack."
So perhaps the square from Chiron to her natal Mars in Leo is another factor here. I'm not too sure what to make of the sextile from the Moon to Neptune, but I mention it because of the timing of the aspect and Brittany's death, as well as the fact that Neptune is the most basic rulership of drugs and since it's not common for a 32 year old to be vulnerable to going into cardiac arrest, one can speculate if drugs were involved, prescription or otherwise. I wonder if this speaks merely (or additionally) to the mystery surrounding her death, so it will be interesting to note what they find that caused her to enter cardiac arrest.
So sorry to hear the passing of this actress.
*From Eileen Nauman's book Medical Astrology, third edition.