Her invite was linked to The Bisexuality Report, which was published by the OU Centre for Citizenship, Identity and Governance (CCIG) last year.
But Meg told Society Matters she felt highly ambivalent about attending the event, because as well as 'highly positive' she sees 'very negative' aspects to this change in the law.
"When we look back a few decades to the time when same-gender attraction was regarded as a psychiatric disorder, and was not allowed even to be discussed in schools, this seems like a huge step forward," she said.
"However there are remaining issues facing LGB&T people that the act does not address; and there are relationship and family issues which the focus on romantic/sexual relationships (whether same or different gender) does not cover.
"People are worried that funding will be withdrawn from LGB&T organisations or that remaining issues will be dismissed.
"It was concerning that the presentations by both David Cameron and Ben Summerskill at Downing Street seemed to suggest that same-sex marriage meant that we had achieved total equality around sexuality."
Also, the same-sex marriage act unfortunately reinforces the idea that romantic and sexual relationships are more valid than any other kind, she said.
"I’m not convinced that commitments between romantic/sexual partners should be regarded as the most important kind of commitment, or the only legitimate basis of families and societies."
Meg explores the issues in greater depth in her blog Rewriting the Rules.
Photo shows Meg (left) with Jen Yockney of BCN at No.10