If the behavior isn’t usual, then rest easier in what is usual for her. Until you get information about what was going on when she wrote that, and why she sent it, you have more of a reason to trust your past experiences with her, than to jump off the deep end and think the worst.
Talk to your partner.
This is not an email conversation. This is a phone or in person (if you live that close) conversation. Mostly, this is a have it soonest conversation. Nothing festers faster than hurt feelings, so you want to get it addressed now.