She definitely need to talk to her doctor before working out. Crunches can be done up to the 8 or 9th month, but after the 1st trimester, the position of the crunches CANNOT be done in the horizontal supine position. Having access to a bench step with several risers on one side will help her elevate her chest. At that late stage, she needs approval from her doctor. The reason for not doing abs during the later trimesters is that it cuts circulation of the uterus and can cause nerves of the spine to be crushed causing a temporary loss of leg functions. There's nothing like trying to get up and your legs falling from under you. Another for not bother doing abs after the 1st trimester is that the abdominal muscles will stretch to fit the size of the baby regardless of how much toning you do. It's important to know that the baby needs the room to move around. Trying to tone the muscles around the belly will only restrict his space.
Kegel exercises are a good thing. They help strengthen the uterus and the hoo-hoo. Forgive me if I start talking in a non-scientific, unanalytical manner. I'm starting to get sleepy again
... anyhow, pregnant women tend to lose control of their urination, esp. when the baby gets bigger. Squeezing the pelvic area will help control the pee. This can be done by non-pregnant women as well. I hear that men love the feeling of having their member squeezed during intercourse. So, anyways, say you sit on the potty getting ready to pee............. WAIT... don't go, yet. Just hold it for 5 seconds. Let some out and squeezed it off and hold it again for 10 seconds. Let go and stop it again one more time. Since pregnant women tend to visit the potty every 20 minutes (sometimes less), they'll be able develop their thingy in a short period of time. I'm proud to say that I can hold it for about a minute and stop mid-stream.
Refrain from using the valsalva maneuver. That will definitely cause her to pass out. Heart rate should not exceed 140 bmp. The baby needs the oxygen more than she does. Do some form of aerobic exercise to keep the heart strong. By the end of her term, she would have gained 20-30 lbs and that could take a toll on the heart. If she's going to lift, eliminate overhead lifts after 1st trimester. It's really important to hydrate. The water will help maintain a comfy temperature for the baby, as well as for the mother. Never go on a diet. Eat whatever, but stay away from caffein, sweetners, and limit excess sugar and salt.
One thing to keep in mind is that exercise during pregnancy is not a guarantee that the pregnancy or labor is going to be much easier.
I'm sure there are more contraindications to write about, but I can't think right now.
best of luck to you.. err your friend