Why shouldn't you be alone when you do a abortion with pills and what if you do it alone anyway?

You are strongly advised to use the medicines in the presence of someone you trust. However, if you choose to do the medical abortion alone, it is not necessarily hazardous. Make sure you are near a phone or some way of contacting medical professionals. You should consider telling someone (a neighbor, a family member, or someone who is nearby) that you are not feeling well and you are going to rest. You can ask them to check on you later in the day after you use the Misoprostol. This way someone will know if you are experiencing complications and can help you, but they do not have to know that you have done a medical abortion. You can say that you think you have had a miscarriage.

More scientific info:

A study that tested the efficacy of medical abortion and the home use of Misoprostol was done in Vietnam and Tunisia. In this study, 22% of the women in Vietnam and 24% of the women in the Tunisian group did not have someone with them at the time they took Misoprostol. This did not result in a higher rate of failures, complications, or side effects.
If a woman is doing a medical abortion, it is better if she can find someone she trusts to be with her during the process. If she experiences abnormally severe side effects (prolonged or extreme pain, bleeding, cramping, fever, nausea, vomiting, diarrhea), she should have someone with her who can get medical help.