How did she send an invitation to her circle of friends for her 70th birthday?

The following is a possible invitation, which you can modify and adjust as needed:

"Dear friends, I am pleased to announce that my mother-in-law is about to celebrate her seventieth birthday! This is a very important milestone, and our whole family hopes to celebrate with relatives and friends on this special day. We plan to hold a grand birthday party for her at [name of restaurant] on [date] and [time]. On this special day, we look forward to your presence and share our joy and happiness. If you can attend, please reply to us before the deadline for reply. We look forward to your visit! "

Please note that the above information should be filled in according to the actual situation, such as date, time, restaurant name, etc. At the same time, don't forget to attach a photo of your mother-in-law to your message to let everyone know who the protagonist is.